应用气象学报

Decadal Variation of the Relationship Between Summer Precipitation along the Huaihe River Valley and SST over the Equatorial Eastern Pacific

Gao Hui

2006, 17(1): 1-9.

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Abstract:
The precipitation along the Huaihe River valley plays an important role for the position and the intensity of the rainbelt in eastern China in summer. Based on monthly rainfall data from 160 primary stations in China during 1951—2003 and the NOAA extended reconstruction sea surface temperatures (ERSSTs) data in the same period, the decadal variation of the relationship between summer precipitation along the Huaihe River valley and the SSTs over the equatorial eastern Pacific is studied. Results show that the precipitation is characterized by a remarkable interannual variability, especially by a quasi-biennial oscillation (QBO) during the 1950s to mid-1960s and after the 1980s. Besides the interannual variation, it also contains a distinct abrupt change in the mid-1970s. The precipitation decreases significantly before the abrupt change time while increases after that. The relationship between the summer precipitation and the SSTs in previous winters over the Niño3 regions also differs remarkably with significant negative correlation coefficients before 1974 but with weak and positive values after 1980. Similar patterns can also be found in the composed global SST anomaly (SSTa) fields according to five wettest and driest years in each period along this valley. A 24-year moving window correlation results reveal that the relation in the last two decades is the weakest among the whole research periods. This weakening relationship can also be found in the SSTa fields in previous autumns. Besides this, the relationship between the precipitation and the intensity of the western Pacific subtropical high (WPSH) also possesses a decadal variation with positive coefficients before 1974 but negative after 1980, especially for that of August. During August, the correlation coefficients between the precipitation and the longitudes of the ridge location of the high are -0.56 and 0.03 respectively in the first and second period, while -0.18 and 0.53 respectively for the intensity of the high. That is to say, the rainfall in August is mainly affected by the position of the WPSH in the first period while by its intensity in the second. Above results indicate that the significance of ENSO as a predictor of the summer precipitation along the Huaihe River valley is weakening and the influencing approach of the WPSH is changing. This weakening significance has increased the difficulties of the prediction of China summer rainfall.

Analysis of the Moist Available Energy of Three Cases of Guangdong Heavy Rain in 1998

Zhou Haiguang, Liu Yanying, Liu Wei

2006, 17(1): 10-18.

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Abstract:
It is well known that the moist available energy (MAE) plays an important role on the broken, development and maintenance of the heavy rain. In order to study the MAE of the Huanan heavy rain and the relationship of the Huanan heavy rain to the MAE, the MAE of three heavy rain fall cases in Guangdong Province in 1998 are calculated using developed formula of MAE, one case is on 14—15 May, the other two cases are on 23—24 May and on 8—9 June. The evolvement and convergence of the heavy rain MAE are analyzed. The space-time relationship between the MAE and the heavy rain is also studied. It shows that the MAE at Guangdong Province and the surrounding area plays an important role on the heavy rain fall period. The high MAE at Guangdong Province supplies the energy for the heavy rain. The low MAE over the middle reaches of Changjiang River helps to form the energy front, at the same time, it can result in heavy rain fall directly or indirectly.The MAE of the heavy rain has quite different in the early and later period of the heavy rain. The evolution of the MAE during the heavy rain procedure oscillates obviously. The MAE is high in the pre-heavy rain period but low after the rain. The difference value between the early and later rain fall period exceeds 6×10⁵ J/m². In order to study the energy threshold of the heavy rainfall, the MAE relative value is defined. This item increases obviously before the heavy rainfall period in the three cases. It indicates that the MAE relative value can reveal the MAE variety characteristic before the heavy rainfall period. As a result, this relative value can be used as a criterion in forecasting the heavy rainfall in the future. The strong rainfall period in the three heavy rain cases is in good agreement with the highest difference value of the MAE between the north and south area. The difference value of the MAE between the north and south area increases because the low MAE value area in the middle reaches of Changjiang River strengthens and moves south wards, which can break the front heavy rain. It means that the low MAE over the middle reaches of Changjiang River plays an important role on the three cases of the heavy rain, it also means that the mid-latitudes is the key regions for the Guangdong heavy rain. The study on MAE convergences of the three heavy rains also shows that the MAE converges at the low and middle troposphere mostly. The MAE convergence at the low and middle troposphere is the main accumulation and supplement of the MAE. It suggests that the strong rainfall period is in good agreement with highest value period of the MAE, at the same time the MAE convergence amount in Guangdong Province is much higher than that over the middle reaches of Changjiang River. In conclusion, the MAE plays an important role on the heavy rain.

Characteristics of the Recent 40-year Flood/Drought over the Middle Reaches of the Yangtze

Wu Xianyun, Ding Yihui, Wang Qi, Ye Chengzhi

2006, 17(1): 19-28.

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Abstract:
Using the Z-index method and the 50-station monthly mean rainfall data over the middle reaches of the Yangtze from Jan 1960 to Dec 2001, the monthly flood/drought grades of each station and the whole region are calculated. Through analyzing the monthly regional flood/drought grades combined with the monthly standard deviation of precipitation, results show that both flood and drought events occur frequently over the middle reaches of the Yangtze during the recent 40 years with average about 1.3 drought months and 1.6 flood months per year, but the frequency and location of flood and drought are quite different from season to season. They mainly happen in midsummer and autumn with a large scale and the Dongting Lake is always among those flood or drought area likely owing to its special landform.Using the EOF (empirical orthogonal function) method, the monthly flood/drought grades of 50 stations from Jan 1960 to Dec 2001 are studied. Based on the first four S-EOFs, the floods/droughts over the middle reaches of the Yangtze are mainly divided into the following four patterns: large scale flood in the whole region, flood in the northwest while drought in the southeast, flood in the southwest while drought in the northeast and drought in the center but flood all around, among which the first pattern is the dominating one whose deviation is much greater than those of the other three. That is to say flood over the middle reaches of the Yangtze is the major one in climate events.The MSSA (multi-channel singular spectrum analysis) method is used to analyze the first 10 S-PCs (spatialprincipal components) generated by the above EOF. It shows that the inter-decadal and inter-annual variations of flood/drought over the middle reaches of the Yangtze are very clear. There is a sharp turning point in the early of 1980s, there are more droughts before and more floods after that period. So, since 1980s, floods occur frequently and become one of the biggest weather disasters over the middle reaches of the Yangtze. At the same time, the flood and drought in the middle reaches of the Yangtze have periodic characteristics of quasi-eightyear, quasi-five-year, quasi-biennial and quasi-quadrennial oscillations. Focusing on the details of the quasi-biennial oscillation of the flood/drought, it is found that it is different from other researches. The flood/drought's quasi-biennial oscillation in the target region is quite regular though its magnitude decreases gradually before the 1980s, but it is not clear after the 1980s.

2006, 17(1): 28-28. DOI: 10.11898/1001-7313.20060104

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Abstract:

Climatic Change of the Green Grass Seasons in Northern Tibet from 1971 to 2000

Du Jun

2006, 17(1): 29-36.

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Abstract:
The climatic change trend of the green grass seasons in northern Tibet is analyzed by calculating the data of mean tem perature, ≥5 ℃ critical temperature and precipitation from 1971 to 2000 in Nakchu district of Tibet. And the maximum potential evaporation is obtained through Penman-Monteith Model in terms of monthly maximum temperature, minimum temperature, wind speed, relative humidity and sunshine duration. The surface humid index is the ratio of rainfall to maximum potential evaporation. The features of seasonal and annual surface humid index are discussed. Main results are as follows: ① The green grass duration is about 80~164 days in Nakchu district of Tibet. The green grass duration is longer in the eastern pasture (over 130 days), where the heat and water conditions are more sufficient. Whereas it is shorter in the middle pasture (less 100 days) where the heat resources are deficient. The mean temperature is 7.5—9.6 ℃ and precipitation is 270—550 mm during the green grass seasons. ② In past 30 years, the mean temperature trend is warming and its increase is (0.18—0.36)℃/10a, especially in mid-western of Nakchu district. The increasing trend of rainfall is insignificant in most part of pastoral areas, but it is significant in Chali. Also, results show that the trend of green grass duration prolongs and ≥5 ℃ accumulated temperature increases obviously in pastoral areas. In general, the climatic trend behaves prolonging duration, warming temperature and increasing precipitation, that is favorable for grass growing. ③ The inter-decadal variations increase in mean temperature. The precipitation is less in the 1970s in most of pastoral areas, more in the 1980s, and it increases in the 1990s compared with that in the former 20 years. In the 1970s, there are later starting date, earlier ending date, shorter duration and lower accumulated temperature (≥5 ℃) during the green grass seasons. But to the contrary in the 1990s, the phase shows earlier starting date, later ending date, longer duration and higher accumulated temperature (≥5 ℃), there are advantageous for grass growth and husbandry production. ④ There are no anomalous years in western Nakchu district in terms of temperature, the anomalous cold years occurres in 1976 in mid-eastern Nakchu, and the anomalous years of precipitation appeared in 1970s. In addition, the accumulated temperature displays anomalous lower in the duration of green grass in most of husbandry districts in middle of the 1970s, whereas anomalous higher years appear in end of the 1990s. ⑤ During the past 30 years, the decrease of annual potential evaporation is significant in the pastoral areas, and the trend indicates a decrease of (10.1—37.8) mm/10a. The potential evaporation decreases more strongly in winter. As for surface humid index, the trend behaves more significant increase. The rate of increasing is (0.02—0.06)/10a.The increase displays strongly in autumn in most of Nakchu district. ⑥ The tendency of warm and humid climate caused by air temperature increasing, potential evaporation decreasing and surface humid index increasing benefits environmental improvement.

A Research on the Applicability of Spatial Regression Test in Meteorological Datasets

Liu Xiaoning, Ju Xiaohui, Fan Shaohua

2006, 17(1): 37-43.

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Abstract:
With the rapid growth of the AWS spatial distribution density, it is more rational to use spatial consistency checks in quality control of meteorological observations of some newly built stations and single element observing stations (i.e. the automatic rainfall stations densely covered all over our country) . For that under these situations traditional historical comparative study and different elements comparing are difficult to do for lacking of data.A new spatial regression checking method used abroad is introduced in detail and applied to spatial checking of some basic surface observing meteorological elements of China for the year of 2003 in order to evaluate the applicability of this approach in China. The method is designed for identification of suspected observing values among neighboring observations. First, some neighboring stations are selected by distance. Second, the root mean square (RMS) errors of the univariate regression equations which are established basing on the examined station observation and neighboring observations are calculated and five reference stations are determined by minimizing root mean square errors. The five reference stations are weighted differentially. Stations with smaller RMS errors get more weighting points. Then, the weighting estimate values and their weighting standard errors of the examined station are computed and used to determine the data range. Data not in this range would be flagged suspected.The spatial checking tests are conducted on 7 basic meteorological elements including daily mean temperature, maximum temperature, minimum temperature, mean vapor pressure, mean wind speed, mean surface temperature and precipitation. The data are obtained from 671 weather stations all over China, and to get more reasonable results the data are divided into 10 districts according to their station designator.Results show that this method works well in identifying errors of single meteorological element especially to the elements with larger spatial variation such as precipitation and wind speed. It should be noticed that there are some differences when applied this method to different areas and different elements. To get a fixed error rate, the values of f should be selected according to the corresponding districts. Finally, same as other spatial checking methods, geographical environment and distribution of neighboring weather stations should be concerned necessarily as influence factors. The approach performs poorer under the condition of sparse station density.

Analysis and Computation on Design Wind Velocity of Sutong Changjiang Highway Bridge

Liu Cong, Huang Shicheng, Zhu Anxiang, Jiang Zhihong

2006, 17(1): 44-51.

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Abstract:

Sutong Changjiang Highway Bridge is the longest cables stayed bridge in the world at present. The correct design wind velocity is highly important to design, construction and operation of the bridge. In order to obtain the reasonable design wind velocity of the bridge, four wind observations are established both on the bank and on the bridge reach of the Changjiang River and both in Nantong and Changshu meteorological observation stations. Further more, a wind observation tower of 80 m in height is also set up on the bank at the same place to measure gradient wind, that is the wind on 10 m, 30 m, 50 m, 70 m, 80 m in height respectively. Wind simultaneous observations in four stations above mentioned and on wind observation tower are then in process from 1st March 2000 to 28th February 2003 to collect the basic data which are necessary for calculating the design wind velocity of the bridge. On the basis of contrasting the corresponding wind data from the four wind observing stations, long series history wind data from nearby meteorological observation station are extended into the bridge reach on the river. By using the gradient data, the variation law of wind velocity with height is studied. As a result, the fitting method of frequency distribution of extreme value is used here to calculate and estimate the reasonable basic designing and engineering wind velocity, which are requisite to the bridge construction. Finally, five conclusions are found as follows.(1) Because of the influences caused by the different geographic environments, the wind velocity of the bridge reach is obviously stronger than that of the nearby meteorological stations, especially the velocities of easterly and northwesterly wind. Generally speaking, the wind velocity of the bridge reach on Changjiang River is about twice as strong as that of the nearby meteorological stations on continent.(2) The wind velocity of the bridge reach on the river surface is also evidently stronger than that on the bank of the river, so that in practical application the wind velocity on the bank can not be substituted for that on the river surface.(3) There is a fine linear correlation relationship between the velocities of the bridge reach and of the nearby meteorological observation stations. When calculating the velocities of the bridge reach, results obtained by using the data of two nearby stations, i.e., Nantong and Changshu observatories, are better than those gained by using the data of one nearby station only. After that, according to insurance probability the confidence interval of design wind velocity is determined.(4) Variation of the wind velocities of the bridge reach with height is in keeping with the exponential law. Here the exponent value is equal to 0.118 which is less than recommended by standards.(5) The wind velocity samples of equal and more than 6 m/s are chosen to compute the basic design wind velocity of Sutong Changjiang Highway Bridge. Though the result of 38.9 m/s is slightly stronger than that simply calculated in the light of standards, the bridge can resist the wind disaster which has return period of 100 years.Therefore, the reliable scientific basis of resistance against wind disaster is provided to making designs for Sutong Changjiang Highway Bridge by the research results of this paper. What is more, the new method of calculating the wind velocity on the river surface developed in the paper may be popularized to other water surface.

Multi-model Consensus Forecast for Temperature

Zhao Shengrong

2006, 17(1): 52-58.

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Abstract:
Based on temperature forecast of operational middle-range model of China, operational model of German meteorological administration, operational model of Japan meteorological agency and temperature observations of China, a temperature consensus forecast system is developed through method of artificial neural network. Product of the system is station temperature forecast of China with 3-hour interval within 72 hours.Forecast modes of summer half year and winter half year are established separately. In order to include most recent impact of data, the process of developing forecast mode runs once a week under the condition of absorbing new data as much as possible.The system has been running stably from 1st of January in 2004. Testing of forecast result from January to May in 2004 indicates that consensus forecast is better than single model forecast. Absolute forecast error of consensus is less than 3.0 ℃ within 72 hours, and it has no systematical error. That means consensus can provide objective forecast support for forecast people. And it also indicates that artificial neural network is a kind of effective method to temperature consensus forecast.Consensus forecast error is different according to different area. It is bigger over Xinjiang and Xizang and smaller over south China and the reaches of the Ynagtze. The cause of this phenomenon is possibly that temperature variability is bigger over Xizang than that over the reaches of the Yangtze. Forecast error of consensus has obvious daily variation. It is always bigger during daytime than in night. On average, the consensus forecast also has forecast ability for temperature changing process with much more argument through contrasting between observation and corresponding forecast result of June in 2004 at partial stations. But the ability of forecast temperature with big argument is poor over the Tibetan area.In order to investigate single forecast impact to consensus forecast, different consensus schemes are developed with forecast results of different schemes checked. Contrasting between different schemes shows that every single forecast with good impacts is important for consensus forecasts results.

An Observational Study on Land-air Interaction over Grass in Guangzhou Panyu Area

Deng Xuejiao, Bi Xueyan, Wu Dui, Liang Jiangyin, Huang Jian, Li Fei, Zhang Hongsheng, Du Jinlin

2006, 17(1): 59-66.

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Abstract:
An introduction is given to the observation of the land-air interaction over grass in Guangzhou Panyu area in 2004. The observational study shows that although the new type three dimensional sonic anemometer has a rain guard net, the error resulted from the effect of raindrop on observation is obvious especially for the u and w direction. The correlation coefficient between

and z/L is low under the rain weather condition, the turbulence intensity and stability has no 1/3 order relationship. The sensible heat flux and latent heat flux calculated by using eddy correlation method are close to those by Bowen ratio energy balance method, the correlation coefficients of sensible heat flux and latent heat flux calculated by the two methods reach 0.8699 and 0.8633 respectively, the errors mainly happen at the period when the surface stability obviously change, namely at noon with maximum of heat flux and at evening or night with minimum of heat flux respectively. The sensible heat flux and latent heat flux calculated by Bowen ratio energy balance method have the relative large positive and negative peaks. The sum of sensible heat flux and latent heat flux (Q_h+Q_e) calculated by eddy correlation method is generally on the side of small, which is not balanced by the available energy (R_n-Q_g) under most circumstances, showing there are some limitations in the surface energy balance equation by neglecting the term of heat storage. The sensible heat flux and latent heat flux have the similar diurnal characters as the solar radiation, the sensible heat flux is larger than latent heat flux in Summer, but the reverse in autumn. CO₂ experiences a diminishing process from May to August, then follow a rising process to a maximum concentration in December, mostly CO₂ concentrations stand at the level of 350×10^-6~400×10^-6.

Characterization of NO₂ Pollution Changes in Beijing Using GOME Satellite Data

Jiang Wenhua, Ma Jianzhong, Yan Peng, Andreas Richter, John P. Burrows, Hendrik NüB

2006, 17(1): 67-72.

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Abstract:
Nitrogen dioxide (NO₂) is known to cause respiratory problems for humans in the urban atmosphere and plays a key role in the control of the strong oxidant such asozone of the atmosphere. Measurements of the global distribution of tropospheric NO₂ column densities have become available with the Global Ozone Monitoring Experiment (GOME) instrument which is launched in April 1995 on board the ERS-2 satellite. The seasonal variation and trend of NO₂ over Beijing is analyzed using monthly averaged tropospheric NO₂ column data from GOME measurements from January 1996 to December 2002. The monthly averaged GOME NO₂ column present distinct variation characteristics with high values in January, February, November and December, and with low values in June, July and August. The results of analysis of GOME data reveal that NO₂ pollution in Beijing had been aggravated from 1996 to 2002 in general, with serious pollution happening in the years of 2002. The highest monthly averaged NO₂ column is found to occur in December 2002 with a value of 3.7×10¹⁶ molecules· cm^-2, increasing by 45 percent and 125 percent with comparison to the highest GOME monthly averaged NO₂ column before December 2002 (that is 2.5×10¹⁶ molecules·cm^-2 in December 1999) and the monthly averaged NO₂ column in November 2002 (that is 1.6×10¹⁶ molecules·cm^-2), respectively. Furthermore, the seasonal variation of GOME tropospheric NO₂ column over Beijing is compared with that of monthly averaged surface mass concentration of NO₂, which are calculated according to the daily pollution index of NO₂ for Beijing for a period from 1 January 2001 to 31 December 2002. Both GOME tropospheric NO₂ column density and surface NO₂ mass concentration present the same distinct seasonal variation characteristics, with high values in winter and low values in summer. It shows that for the comparison period the variations of monthly averaged tropospheric NO₂ columns over Beijing are well consistent with the variations of the monthly averaged surface NO₂ mass concentrations in Beijing. The correlative coefficient is as high as 0.86. It can be concluded that GOME tropospheric NO₂ column data can be used to analyze the seasonal variation and trend of NO₂ pollution over a specific region.

Error Analysis on Tropical Cyclone Official Forecast in the Northwest Pacific from 1999 to 2003

Qi Liangbo, Huang Danqing, Yu Hui

2006, 17(1): 73-80.

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Abstract:
Based on the official forecasts of tropical cyclone (referred as TC hereinafter) in the Northwest Pacific from 1999 to 2003, real time error analysis is carried out for China Central Meteorological Observatory (CMO), Japan Meteorological Agency (JMA) and Joint Typhoon Warning Center (JTWC). Five aspects such as total error, annual error, different sea-areas, different tracks and different intensity trends are considered to compare the error characteristics of each forecast center in detail. Evidence suggests that JTWC's path error is the least and JMA has the best behavior in intensity forecast from a view of 5-year average. In great probability, all centers may overestimate TC's intensity, but when underestimating occurs, the bias always turn out to be a bigger one. After the year of 2000, all centers' performances improve greatly. As for CMO, Its track errors are less than 150 km (24 h) and 250 km (48 h) respectively. Over different see-areas, there is always a better path forecast among the three centers:JTWC behaves better at West-Luzon area. JMA has a overwhelming superiority on others at Che ju area. Its 24 h error is just 88 km, while the others produce an average of about 130 km. At South-Ryukyu area, JMA and JTWC perform obviously better than CMO whose track bias averages out to 155 km in 24 h and 340 km in 48 h forecast, while others just make out a value of 110 km and 280 km respectively. In most cases, JMA's intensity forecast is the best, but there isn't a obvious gap between CMO and JMA. JTWC's result is the poorest. As to different TC tracks, except for those veering at South China Sea, JTWC's path forecast is often the best. For intensity forecast, all centers make poor behaviors in turnabout track, while JMA and CMO perform better in Veering-after-landing and Northeastward tracks. For tropical cyclones with different intensity trends, JTWC mostly gives out a better path, especially for rapid intensification cases. Generally, all members make poorer path forecast for weakening cases. Intensity error of steady TC is the smallest, while that of rapid intensification is particularly bigger than others. That means more attention should be paid on researching and forecasting of rapid change TC, including rapid intensifying and rapid weakening.These results help to understand entirely forecast qualities of the three main forecast centers and give some guidance for forecasters when they make references on these centers' forecast results, and above statistics and analysis can be either a base or a direction for concerning research.

A Contrast Test of the Methods to Remove the Analyzed Typhoon

Huang Xiaogang, Fei Jianfang, Lu Hancheng

2006, 17(1): 81-86.

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Abstract:
The theories about removing the analyzed typhoon which used in GFDL hurricane model and MM5 model are introduced in detail. The GFDL model uses a sophisticated filtering scheme, and the filter domain defining the location and extent of the tropical cyclone in the global analysis is determined from the distribution of the low-level disturbance winds. Each level's filter domain is same and there is no correlativity in the fields. The MM5 model modifies the vorticity, geostrophic vorticity, and divergence, then solve for the change in the nondivergent stream function, geopotential and velocity potential and compute a modified velocity field. The MM5 scheme sets the radius same so that the analyzed typhoon features may be removed more or less for various cases. The comparison analysis about ten cases shows that, owing to the error in data and bought from the projection, the location between two levels has big departure for some cases, and make the fields cannot be removed reasonably, such as temperature. So the method seeking the analyzed typhoon center and radius in the average meaning used by GFDL is more advantageous, on the other hand, the harmony of fields is considered in MM5 scheme, and it is more reasonable than GFDL in this facet. The modified method which correcting MM5 scheme through combining these two schemes' advantages is also tested for these cases and the results showed the analyzed typhoon may be removed more reasonably and thoroughly.

Climatic Suitability of Cotton and Its Changes in Henan Province

Ren Yuyu, Qian Huaisui

2006, 17(1): 87-93.

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Abstract:
Cotton is an important economic crop for Henan Province. With long growth season, cotton is sensitive to climate change, so its climate suitability in Henan Province comes to be a valuable research. Combining previous researches and existent climatic suitability models, the cotton climatic suitability model suitable to Henan Province is established. According to homogenize principle, 46 stations in Henan province are chosen. With meteorologic data from 1960 to 2000, the cotton climatic suitability degrees of these stations during 1960—2000 are calculated and the mean is used as the general cotton climatic suitability of Henan Province. The result shows that the cotton climatic suitability degree in Henan Province has a declined tendency, particularly the latter twenty years. To explore the reason of this phenomenon, the changes and their impact on suitability of the climate elements (precipitation, sunshine hour and temperature) in the five growth seasons are analyzed. The final result shows that the decline of precipitation suitability in seedling stage is the main reason of this decline. Then the tendency and intensity of the suitability change in each station during 1980—2000 are calculated. The result shows the change situation embodies strongly regional character. The suitability change tendencies in the mountainous areas of the Nanyang Basin and in the subtropical regions south to the Huaihe River decline and in plain areas increase while the change tendencies in areas north to Huaihe River are reverse, i.e. the tendencies in most plain areas of Henan Province from Huaihe River to the Yellow River decrease and in mountainous areas increase. To areas north to the Yellow River, the character of change tendencies is like the subtropical regions:the mountainous areas have decrease tendency and the plain areas have increase tendency. From the south to the north in Henan Province the Huaihe River and Yellow River are the board line of different suitability changes tendencies. Based on the cotton climate suitability of the stations during 1980—2000, the change tendencies in Henan Province are divided into three styles:the rash increase style including Funiu mountainous areas and Taihang-Wangwu mountainous areas; the weak increase style including the Yudong Plain, Funiu-Tongbai plateau areas and the Nanyang Basin; the decrease style the rest areas. Lastly with the precipitation, sunshine and temperature data during 1980—2000 in the 46 stations the processes and reasons of the climate suitability changes in different areas are analyzed. For example, the increase of precipitation deviation in bud stage is the main reason of the suitability decrease for the Yudong Plain while the increases of temperature and sunshine hour in boll stage in the Funiu mountainous areas make the climate condition more suitable to the cotton growth.

A Study on the Forecast Method of the Low Visibility Weather of Shuangliu Airport

Feng Hanzhong, Chen Yongyi, Cheng Yongqin, Luo Kesheng

2006, 17(1): 94-99.

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Abstract:
At Shuangliu International Airport the frequent, long-time low visibility often leads to the delay of scheduled flight and affects the safety of the planes. With the development of social economy and the air transport, the low visibility weather of Shuangliu Airport arouses great concern of the air control authority of the airport. Because a number of the factors can result in the low visibility weather, the factor mechanism is complex, and meanwhile the correlativity between the factors and the low visibility weather is insignificant, meteorologists are concerned most about how to forecast such weather as possible as they can. While there are huge amounts of information, the relation between the forecast object and the factors is unclear. Given this, intelligent machine learning technique is a good method to solve this sort of problems. In order to improve the forecast, Support Vector Machines (SVM), an intelligent machine learning technique that can solve the nonlinear problems is employed in the research to study the forecast method of the low visibility weather of the Shuangliu Airport. SVM method nonlinear is mapped by kernel function from lower dimensional space to higher. The higher nonlinear correlativity between the factors and the forecast object is indirectly expressed in implicit expression. Finally, the dependence of the factor and the object is depicted, and the model is set up by support vector. Hence, the model is not only related to the forecasting factor, but the kernel function as well. By using the data from Chengdu radiosound observatory and Shuangliu Airport surface observatory through 1997 to 2001, the forecast models of low visibility weather of Shuangliu Airport are built by mean SVM method with several kernel functions. Test results show the forecast model constructed with the radial base kernel function and the forecast model constructed with Laplace kernel function are better than the others, in which Threat Score are 0.287 and 0.292 separately, far above the frequency (0.155) of low visibility weather occurring at Shuangliu Airport. Test results also show, in the SVM model constructed with the radial base kernel function, the false alarm is higher and the omitted alarm is lower; in the SVM model constructed with Laplace kernel function, it is opposite. Therefore, if the accuracy of low visibility weather forecast is emphasized, the model constructed with Laplace kernel function should adopted; but if the precaution is emphasized, the model constructed in radial base function should be selected.

Quantitative Detection of Bosten Lake Area Using NOAA/AVHRR Data

Liu Ruixia, Liu Yujie, Zheng Zhaojun, Huang Yanbin

2006, 17(1): 100-106.

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Abstract:
To estimate the area of Bosten Lake and the area change since 1990, the threshold values of the channel reflectance and bright temperature of NOAA/AVHRR data are used to distinguish water body from other objects. For channel 2, water body indicates lower reflectance than vegetation and other land covers. The ratio of Channel 2 to Channel 1 can enhance the difference between water body and land, and decrease the effects of cloud and vegetation to a certain extent. For the image in April, the water body is identified by the reflectance of Channel 2 and the ratio of channel 2 to channel 1. The pixels are identified as water body if the reflectance in channel 2 is lower than the threshold T₁, as the land if it is higher than T₂ (threshold), and as mixed pixels if it is between T₁ and T₂. Based on the histograms of channel 2 and the ratio of channel 2 to channel 1, the threshold values of the T₁ and T₂ are found, and they are fixed on the different satellite images. In October, the water body in the south-east of the Lake is identified with bright temperature of channel 4 because the region is covered by vegetation. But, in the east of the Lake, the water body is still identified by the reflectance of channel 2 and the ratio of channel 2 to channel 1. The threshold value of channel 4 is also determined according to the histogram. The linear mixed model is used to calculate the area of mixed pixels at the edge of lake. The area of Bosten Lake in April and October from 1990 to 1998 are calculated, and the area changes of Bosten Lake during the nine years are detected. The result shows that the area of Bosten Lake has been increasing from 1990 to 1998 due to the increasing of the temperature/precipitation and the decreasing of evaporation, and the water utilization by mankind and the water exiting has been stable, even has decreased since 1988. Furthermore, the area of Bosten Lake is bigger in spring than that in autumn due to the supplying of the melt water of snow after the winter.

The Inter-decadal Change of SSTA Interaction Between the Tropical Pacific and Indian Ocean in Winter/Summer

Fan Lingli

2006, 17(1): 107-112.

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Abstract:
The tropical Pacific sea surface temperature inter-annual anomalies (SSTA) are analyzed in terms of NCEP/NCAR reanalysis and GISST 2.3b datasets using EOF technique analysis, results show that the Niño3 index can be used to express the tropical Pacific sea surface temperature inter-annual anomalies. 11-year moving correlation coefficient of the Niño3 index and the tropical Indian Ocean SSTA is used to reflect the relation between the tropical Pacific and the tropical Indian Ocean SSTA inter-decadal changing, because ENSO thrives in winter and Dipole thrives in summer, so its inter-decadal changing is studied in winter and summer. Results indicate that the difference of the moving correlation coefficients spatial distributions in two periods 1951—1976 and 1977—2000 is dominant. In winter, the signal of ENSO is same over whole tropical Indian Ocean (moving correlation coefficients are positive from west to east), during 1951—1976 period the intensity of correlation is stronger than the latter period, the possible reasons are as follows:firstly, the winter is the ENSO prime season, the second is in 1977—2000 period the warmer center of the tropical Pacific moves to east, then the Walker circulation updraft also moves eastwards, therefore the two vertical zonal circulations (the Walker circulation and the monsoon circulation) couple weakly. In summer the moving correlation coefficients spatial pattern differences from the winter spatial pattern, moving correlation coefficients are positive in the west tropical Indian Ocean, and moving correlation coefficients are negative in east tropical Indian Ocean, that is Dipole, but the gradient of the west tropical Indian Ocean moving correlation coefficient and the east tropical Indian Ocean moving correlation coefficient enlarges in the later period, the possible reasons are:Dipole thrives in summer, ENSO develops in summer, and the warmer center of the tropical Pacific moves eastwards in the later period, but the Walker circulation updraft moves to east slightly, and the intensity of the monsoon circulation and the Walker circulation updraft powerful place is strengthened, therefore the two vertical zonal circulations couple intensely. That is the inter-decadal variations of the interaction between the tropical Pacific and the tropical Indian Ocean SSTA are remarkable, in the different season, the inter-decadal variation tendency is not alike, it is mainly created by the tropical Pacific and the tropical Indian Ocean climate background field decadal oscillations.

An Open Model of Operational Product System for China Weather Radar

Liang Haihe, Gao Yuchun, Liu Liping, Li Bai, Jing Zhongqi, Xu Baoxiang

2006, 17(1): 113-118.

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Abstract:
China Doppler weather radar (CINRAD) network consisting of 158 radars with S and C bands is being built. Radar meteorological products exploitation and data applications are getting more and more imminent and necessary with the development of CINRAD; meanwhile, NEXRAD open system plan is being implemented. So the CINRAD operational model and product system infrastructure are key and important issues.CINRAD characteristics and development requirements are analyzed, and an open model of operational application system and data distribution for CINRAD is presented. The CINRAD has 6 type radars with S and C band made by 3 factories, so it is needed that very good interfaces for different scan patterns, data formats, and excellent development and test environment for different algorithms, and integrative processing and display system for different wave bands and many kinds of observation data. CINARD has lots of users on weather forecast, weather modification, hydrometeorology and traffic management etc, so it is necessary that software update and continuous developments of algorithms, and it is required that open and distribution structures. In terms of China meteorological operation model and CINRAD status, it is advanced that distribution products operations model and base data transport scheme. And it is also designed that the intrastructure and operating mechanism of open product system for CINARD.The existing NEXRAD ORPG is an open and loosely-coupled system, it supports other systems and algorithms to be operating together by parallel interfaces, and the Linear-Buffer supports separate modules data communication, so that CINRAD Radar Product Generator (CRPG) is designed as a compatible system with ORPG. The OPRG, CRPG and their low-level interface libraries are encapsulated with a new control interface which connected by Radar Data Acquirement (RDA) and Meteorological Information Comprehensive Analysis and Process System (MICAPS). The open and distribution radar product scheme is helpful to other meteorological software systems of China.

Impact of Chilling Temperature and Drought on Corn Physiological Process in Seedling Stage

Zheng Jiangping, Wang Chunyi

2006, 17(1): 119-123.

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Abstract:

Northeast China is a frequently occurring area of agricultural meteorological disasters, where chilling temperature and drought frequently happen simultaneously, which brings about a greater impact on the growing up process and grain yield of corn and other crops. Therefore, they are paid more attention to. However, the researches in the past are mostly of the single weather disaster of either chilling damage or drought, seldom considering their combining impacts on corn growing up process. From this view point, combining impacts of chilling damage and drought on corn physiological process are undertaken with its growing up process in seeding stages.The experiment is carried out in the artificial weather laboratory of crops cultivating institute of Heilongjiang Agricultural Academy in 2004, where the mode of cultivating corn in a pot is adopted and the corn being cultivated is treated with chilling damage and drought respectively in its seeding stages. Through artificial simulation experiment, the impact of chilling damage, drought and their combining on corn physiological process, growing up process in seeding stages are quantitatively studied. Results are as follows:the impacts of chilling damage on photosynthesis and transpiration rate are both negative effects; photosynthesis rate assumes a conic section correlation with temperature. Transpiration rate assumes a cublic section corvelation. When the field water capacity is 80% and the temperature drops from 20 ℃ to 16 ℃, photosynthesis rate decreases by 22.4% and transpiration rate decreases by 44.0%; impacts of drought on photosynthesis and transpiration rate are also negative effect; both photosynthesis rate and transpiration rate assumes a conic section correlation with soil moisture. when the temperature is 20 ℃, the photosynthesis rate decreases by 11.5% from 80% of field water capacity to 50% and transpiration rate decreases by 2.7% from 60% of field water capacity to 50%; the combining impacts of chilling damage and drought are far greater than the impacts of single factor of chilling damage or drought; the photosynthesis rate decreases by 32.1% and the transpiration rate decreases by 52.7% when the temperature drops from 20 ℃ to 16 ℃ accompanied by the soil moisture decreases from 80% of field water capacity to 50%.

The Application of Set Pair Analysis on City Air Pollution Index Forecasting

Zhu Xiaoming, Wang Guoqiang

2006, 17(1): 124-128.

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Abstract:
The predictors of city air pollution forecast models which are specially selected have prefer forecast ability in general. But sometimes when the situation changes, some predictors are negative and may result in failure of the forecast model. According to the principle of Set Pair Analysis (SPA), regarding uncertainty and certainty as a dynamic systematic procession, the evolution of predictors' action in every forecasting is analyzed and processed dynamically. That is to say, the judgment of potential states and Identical-Discrepancy-Contrary Analysis are made about predictors before being used to calculate weather forecast, then the effect of predictors on weak potential state which may interfere forecasting is suppressed effectively, while those predictors on strong potential state which may be contributed to forecasting is given full play. As a result the dynamic evolution in the structure of predictors is made in the forecast model, and the rationality of forecasting mechanisms and the ability of models are intensified. So adding the processing uncertainty to the forecasting model is help to improve the forecasting accuracy.

Vol.17, NO.1, 2006