Shuhui ZHAO,Yang LIU,Jian YUAN,Bin FANG,Xin QIN,Yanzhe LI

Liaoning Provincial Weather Modification Office,Shenyang 110066,China

Assessing the Precipitation Enhancement Development Potential in 2013 Using the CWRPEP Method in Liaoning Province

Shuhui ZHAO,Yang LIU,Jian YUAN*,Bin FANG,Xin QIN,Yanzhe LI

Liaoning Provincial Weather Modification Office,Shenyang 110066,China

[Objective]The research aimed to assess the development potential of artificial precipitation in Liaoning Province.[Method]The evaluation method of cloud water resource for precipitation enhancement potential was used.[Result]The annual total precipitation enhancement potential by cloud water resource in the air in 2013 was 1.23 billion tons in Liaoning,and cloud water resource for precipitation enhancement was 1.63 billion tons.[Conclusion]The spatial and temporal distribution for development potential of cloud water resource in the air was very uneven in Liaoning Province,and the mainly period was during spring and autumn.It will be received obvious effect in the two seasons.In order to compensate for the restriction of the operational capability lack on cloud water resource development,we need to continue to improve the operation capacity building.

Cloud water resource;Precipitation enhancement;Potential

A tmospheric water resources in China are more abundant,and its development and utilization potential is great.According to the statistics,60 billion-280 billion tons of precipitation could be increased in China every year,that is,development potential of atmospheric water resource in China can reach 280 billion tons every year,which is equivalent to 7 times of the Three Gorges Reservoir capacity[1-2].As the introduction of central document No.1 in 2011,the topic about scientifically developing the cloud water resource in the air becomes the focus,which is also a key work of meteorological department.To implement the spirit of central document No.1 and enhance the development and utilization of cloud water resource in the air,Weather Modification Center of China Meteorological Administration issued cloud water resource for precipitation enhancement potential method,which is called as CWRPEP method for short,and required its application in whole country.Assessment on cloud water resource has important role and significance on the implementation of weather modification work and benefit evaluation.In 2005,distribution condition and development potential of cloud water resource in Liaoning Province were analyzed by using conventional sounding,observation data of cloud and precipitation.It was thought that there were more operation opportunities and greater precipitation enhancement potential[4-6].It was conductive to effective implementation of routine business work of precipitation enhancement to use CWR-PEP method to further study temporal-spatial distribution of cloud water resource in Liaoning Province.

Introduction of CWR-PEP Method and Parameter Setting

Assessment scheme of cloud water resource for precipitation enhancement potential can be expressed as:

PEP=Hh×Ew×Pe=∑(Hht×Hhs)× Ew×[Pc×Pn×(1-Pk)×Pa].

Total precipitationHh

Hh=∑Hht×Hhs.Here,Hh is total volume(mass)of precipitation in region S at time interval T;Hht is total thickness of precipitation within time interval T observed by each station; Hhs is the area represented by the station;the product of Hht and Hhs is precipitation volume(mass)observed at the station;∑is the sum of precipitation volume(mass)of each station in region S.When the units of Hht and Hhs are respectively mm and km2,the units of PEP and Hh are×103t.According to Administrative division, Liaoning Province administrates 14 prefecture level cities,17 county level cities,19 counties and 8 autonomous counties.Precipitation data at corresponding meteorological observatories of 58 cities and counties were used to calculate,and monthly and annual precipitation(mm)and total precipitation (×103t)in whole province could be obtained.

Precipitation enhancement efficiencyEw

A lot of test results showed that the mean of precipitation enhancement efficiency was 10%-15%.During "the 11thFive-year"period,778 paired samples were contrasted and analyzed by using regional contrast test method in"Research on Integrated Key Technology of Practical Catalytic System for Precipitation Enhancement"from Key Project of Liaoning Provincial Department of Science and Technology.Results showed that under guaranteed rate of 80%,precipitation enhancement efficiency was 25.4%when relative to natural rainfall and was 20%when relative to rainfall after artificial influence.Under guarantee rate of 90%,precipitation enhancement efficiency was 17.9% when relative to natural rainfall and was 15%when relative to rainfall after artificial influence.In the assessment scheme,we directly used the research result,and set precipitation enhancement efficiency as 15%.

Precipitation enhancement probabilityPe

Precipitation enhancement probability refers to the proportion of region and period for precipitation enhancement,and calculation formula is:Pe= Pc×Pn×(1-Pk)×Pa.Here,Pc is the occurrence probability of suitable condition.According to cloud condition requirement of precipitation enhancement,occurrence probability of cloud condition meeting precipitation enhancement in the assessed region and period is summarized.Pn is demand probability.Under the situation meeting suitable condition,it is the proportion of demand operation which can form significant socio-economic benefit when increasing rainfall in the region at the time.Pk is the probability not suiting for operation.We should avoid local disaster risk brought by operation,such as local flood or mud slide caused by rainstorm and drought-flood rapid conversion.Pa is operation realizing probability.For precipitation cloud region with suitable zone and opportunity,due to the limitation of operation ability,a part of cloud region is operated,and its proportion is Pa.Pe is the intersection of four probabilities, and the calculation of each probability is restricted by the last probability. Based on sufficiently considering calculation efficiency in Liaoning Province,calculation sequence was determined:Pk,Pn,Pc and Pa.

Probability not suitable for operationPkSeen from actual situation of precipitation enhancement operation in Liaoning Province over the years, the situation not suitable for operation often appears in the period with more precipitation in flood season.To avoid local disaster risk,provincial government requires stopping operation.In addition,winter snowfall induces general concern of the community.On the one hand,snowfall will bring various negative influences to urban traffic.On the other hand,moisture adding effect of winter precipitation on spring soil is not great in Liaoning Province.Under general situation,snow enhancement operation is not carried out.So,it is thought that the above two kinds of situations are both not suitable for operation.During assessment period (November of 2012 to October of 2013),snowfall period was from November 3,2012 to April 17,2013, and flood season was from July 1, 2013 to September 7.The above two periods were not suitable for precipitation(snow)enhancement operation.

Operation demand probabilityPn

Major demands of Liaoning Province implementing precipitation enhancement operation include agricultural drought resistance,reservoir water storage and declining forest fire disaster grade.So,operation demand probability mainly considers soil water demand,reservoir water demand and forest fire disaster.Soil water demand situation uses hourly automatic soil moisture observation data at 53 stations of Liaoning Province.Because that major crop in Liaoning Province is corn,and relative humidity of soil from surface to 30 cm deep has great impact on corn,the mean for relative humidity of soil at 0-10,10-20 and 20-30 cm in 24 h is counted as relative humidity of soil at the station on the day.When relative humidity of soil is less than 80%,it is thought that soil needs water,and there is precipitation enhancement demand,or else,it is unwanted.Reservoir water storage is originally listed one of the factors taken into account for operation demand probability,but due to not obtaining corresponding data,the factor is not used in the assessment.The demand for declining forest fire disaster grade mainly refers to issue information of forest fire disaster grade.When forest fire disaster grade is more than Grade 3,it is easy to burn.Then it has the demand for declining forest fire disaster grade,or else,it is unwanted.When a factor shows that there is precipitation enhancement demand in the region,it is thought that there is operation demand on the day,or else,there is not operation demand.

Probability occurring under suitable conditionPcCurrent precipitation enhancement operation ability in Liaoning Province only limits in catalyzing cold cloud and mixed cloud,and catalytic operation of warm cloud is still at test stage.So,suitable condition of operation considers cold cloud or mixed cloud.In addition,to make precipitation enhancement operation generate proper social benefit,we also should consider its input/output ratio.If precipitation does not reach certain magnitude,we do not consider implementing operation generally.So,judging indexes of suitable condition are set:e-Ei＞0 and daily rainfall＞3 mm. Except daily rainfall data,e-Ei indexes at 500,700 and 850 hPa are judged by numerical forecast product of WRF mode.When there is a layer meeting judging condition and continuously occurring for more than 2 h,it is thought that it is suitable for operation on the day.

Operation realizing probabilityPa

Liaoning Province rents 3 airplanes and 218 mobile rocket launching system every year,and implements cross regional joint operation in whole province.So,under the situation that all airplanes and rockets carry out operation,it is thought that it could meet basic requirement of operation in whole province.In addition,due to strong airspace safeguard,the situation can not work limited by airspace is seldom.It is thought that operation realizing probability under normal situation is 100%.According to rent period of airplane and work period of rocket, corresponding operation realizing probability is calculated.

Assessment Results

Rainfall

Total annual rainfall in Liaoning Province in 2013 was 115.4 billion tons,and annual average rainfall was 782 mm.In 58 cities and counties of whole province,total rainfall was from 0.1 billion to 8.2 billion tons,and average rainfall was during 300-1 500 mm. Seen from Fig.1,total rainfall obviously presented decreasing tendency from southeast to northwest.Total rainfall in southeast Liaoning was greatly more than other regions,and total rainfall in Chaoyang,Huludao,Jinzhou,Yingkou and Panjin was less.Total annual rainfall in more than 30 cities and counties concentrated from 1 billion to 3 billion tons.Seen from annual average rainfall,the maximum was 1 457.9 mm in Dandong City,while the minimum was only 324.1 mm in Beipiao City of Chaoyang.The city with annual average rainfall less than 900 mm accounted for 74.14%.

Via statistical analysis,it is thought that precipitation is the determinant factor affecting water resource condition[4].Liaoning is in north temperate continental monsoon climate region.The special geographical position and climate condition decide that Liaoning Province naturally lacks water resource.Besides uneven spatial distribution of precipitation,temporal distribution also has great difference. Precipitation mainly occurs in summer, and general rule is abundant water in flood season and lower water in other periods.The situation in 2013 was also the same(Fig.2).During assessment period,rainfall in July was 252 mm and was the maximum,which accounted for 33.29%of total annual rainfall. Rainfall during major flood season was 403 mm,which accounted for 53.29% of annual rainfall.

PEP

PEP of cloud water resource in the air over Liaoning Province was 1.23 billion tons in 2013,and spatial distribution of PEP in whole province was shown as Fig.3.Potential value in east Liaoning was bigger,and PEP in Xinbing County of Fushun City reached 0.093 billion tons.Major reason for lower PEP in west Liaoning was less total rainfall,and lower PEP in south Liaoning was because of small demand probability.PEP area mean in whole province was about 8 mm,in which the value in Fushun, Shenyang,Benxi and Tieling could reach over 15 mm.In whole westLiaoning region except some areas of Fuxin,PEP area mean was all less than 5 mm.On the one hand,rainfall was less.On the other hand,because that occurrence probability of suitable operation condition was small,PEP area mean in the zone was lower. Rainfall in Dandong and Dalian was abundant,and small demand probability was direct reason for small PEP.

CREP

CREP is the calculated value in CWR-PEP under the situation not considering operation realizing probability.CREP distribution of precipitation enhancement at 58 cities and counties in whole year was shown as Fig.4. CREP sum of whole province was 1.63 billion tons,in which CREP in Fushun,north Tieling and south Shenyang could reach 0.06 billion tons,which was abundant,and CREP in other most areas was less than 0.04 billion tons.

Because that the difference between PEP and CREP mainly embodied in operation ability,seen from Fig. 5,rent time of airplane had great impact on PEP from May to September when cloud water resource was abundant,and 0.389 billion tons of cloud water resource for precipitation enhancement was not developed and used well.In October,cloud water resource for precipitation enhancement was 0.624 billion tons,which was still abundant.But due to rent time expiring of airplane,half of cloud water resource for precipitation enhancement wasted.

Conclusions and Discussion

Total precipitation enhancement potential by cloud water resource in the air over Liaoning Province was 1.23 billion tons in 2013,and cloud water resource for precipitation enhancement was 1.63 billion tons. Temporal-spatial distribution for development potential of cloud water resource in the air was very uneven in whole province,and the mainly period was during spring and autumn.It will be received obvious effect in the two seasons.In addition,we need to continue to improve the operation capacity building to compensate for the restriction of the operational capability lack on cloud water resource development.

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Responsible editor:Ping SONG

Responsible proofreader:Xiaoyan WU

CWR-PEP方法評(píng)估2013年遼寧省人工增雨開發(fā)潛力

趙姝慧，劉旸，袁健*，房彬，秦鑫，李炎喆
（遼寧省人工影響天氣辦公室，遼寧沈陽110066）

[目的]評(píng)估2013年遼寧省人工增雨開發(fā)潛力。[方法]采用云水資源人工增雨開發(fā)潛力評(píng)估方法。[結(jié)果]2013年度遼寧省空中云水資源人工增雨潛力總量為12.3億t，人工增雨云水資源量為16.3億t。[結(jié)論]遼寧省空中云水資源可開發(fā)潛力時(shí)空分布非常不均，可開發(fā)潛力較大的時(shí)段主要是春季和秋季，加大這兩個(gè)季節(jié)的空中云水資源開發(fā)力度可以收到明顯成效。加大遼寧省作業(yè)能力建設(shè)可以彌補(bǔ)作業(yè)能力的不足對(duì)云水資源開發(fā)的限制。

云水資源；人工增雨；潛力Precipitation enhancement potential= Total precipitation×Precipitation enhancement efficiency×Precipitation enhancement probability.If using PEP to represent precipitation enhancement potential,Hh to represent total precipitation,Ew to represent precipitation enhancement efficiency and Pe to represent precipitation enhancement probability,assessment formula can be written as:

遼寧省氣象局科研課題“完善云水資源人工增雨開發(fā)潛力評(píng)估方法（CWRPEP）”。

趙姝慧（1982-），女，遼寧鞍山人，工程師，碩士，從事人工影響天氣方面研究，E-mail：zhaoshuhui512@163.com。*通訊作者，高級(jí)工程師，從事人工增雨業(yè)務(wù)工作，E-mail：yj1962@126.com。

2015-03-20

修回日期 2015-05-20

Supported by"Perfecting CWR-PEP Method"from Science Research Project of Liaoning Provincial Meteorological Bureau.

*Corresponding author.E-mail:yj1962@126.com

Received:March 20,2015 Accepted:May 25,2015