| The fifth assessment report of the Intergovernmental Panel on Climate Change(IPCC)of the United Nations Intergovernmental Panel on Climate Change pointed out that the climate of the earth has changed a lot in the past 60 years.The temperature of the earth has generally increased and the frequency of extreme climate event has increased.Climate change has affected all aspects of ourlives,and it has become a major issue in the world in the 21 st century.Underlying surface changes caused by human activities are important factors affecting climate change.Underlying surface changes in river waters will also affect local climate.Wujiang is the largest river in Guizhou Province and one of China's hydropower energy bases.The cascade development of the main stream of the Wujiang River has caused significant changes in the water area,and changes in the water area will inevitably lead toc hanges in the landland thermal difference.It is of scientific and practical significance to conduct research on the impact of changes in watershed area in Guizhou on climate change at the regional scale.In this paper,the Wujiang River Basin(in Guizhou)is used as the research area,and the remote sensing images of the Wujiang River Basin in 1983,1990,1995,2000,2005,2010,and 2015 and47 meteorological stations in the Wujiang River Basin from 1983 to 2015 Annual air temperature,precipitation,wind speed,relative humidity,and sunshine hours are used as data sources.On ArcGIS10.2.1 and ENVI5.3 software platforms,the normalized water body index method(NDWI)was used to extract the water area of the remote sensing image,and ArcGIS was used to vectorize the waterarea,and the water area data was obtained by statistics.Summing up and averaging the temperature,precipitation,wind speed,relative humidity,and sunshine hours of 47 meteorological stations in the Wujiang River Basin from 1983 to 2015 to obtain the annual avera ge temperature,annual average precipitation,and annual average wind speed for each year,Annual average relative humidity,annual average sunshine hours.Analyze and study the climate effect of water area changes from two angles,one is to superimpose the water area change of the entire Wujiang River Basin from 1983 to2015 and the annual average of each meteorological factor,and use the national climate change as a reference for comparison The second is to conduct research by selecting typical counties and comparing the monthly and seasonal changes of meteorological factors in typical counties.The following conclusions are drawn:(1)From 1983 to 2015,the water area of the Wujiang River Basin generally showed an upward trend.In 33 years,the water area increased by 47.649km2,an increase of 21.68%.(2)From 1983 to 2015,the annual average temperature,annual average maximum temperature,and annual average minimum temper ature in the Wujiang River Basin all showed an upward trend,and the annual average precipitation,annual average wind speed,annual average relative humidity,and annual average sunshine hours all declined trend.(3)When the water area of the Wujiang River Basin increased from 1983 to 2015,the annual average temperature,annual average maximum temperature and annual average minimum temperature also increased.The yearonyear average temperature change is large in years with rapid growth of water area,and the yearonyear avera ge temperature change is small in years with slow growth of watearea.However,the change in the annual average temperature of the watershed is very consistent with the change in the national average annual temperature.Therefore,the change in the annual average temperature of the Wujiang River Basin is largely affected by the national background climate,and is less affected by the changes in the water area.(4)When the water area of the Wujiang River Basin increased from 1983 to 2015,the average annual precipitation generally showed a downward trend,but the decrease was not large.However,when viewed in different time periods,the annual average precipitation in most years of the increase in the water area of the Wujiang River Basin also showed an upward trend,and in the years when the water area changed,the average annual precipitation increased by a large amoun t.There is a big difference between the annual average precipitation change in the basin and the national average precipitation change,which shows that the annual average precipitation change in the Wujiang River Basin is largely not affected by the national background climate,but the climate effect of the watershed area change.(5)When the water area of the Wujiang River Basin increased from 1983 to 2015,the annual average wind speed showed a general downward trend,but the decline was not large.The surface of the water body is smoother than the land surface.When the windblows on the smooth water surface,the resistance is less,the waterarea increases,and the wind speed should also increase.However,the results of this study are reversed.This is largely due to the influence of the topography of the study area.The study area is a typical southwestern karst landform with large terrain fluctuations,and its influence on wind speed cannot be ignored.(6)When the water area of Wujiang River Basin increased fro m 1983 to 2015,the annual average relative humidity showed a ge neral downward trend,but the decline was not large.However,whe n viewed in different time periods,the annual average relative humi dity in most years of the increase in the water area of the Wujiang River Basin tends to increase,and the increase in the annual avera ge relative humidity in the year when the water area changes.The change in the annual average relative humidity of the river basin is quite different from that of the national average annual relative humidity.This shows that the annual average relative humidity of the Wujiang River Basin is largely not affected by the national background climate,but the climate effect of the watershed area change.Can play a role in humidification.(7)When the water area of Wujiang River Basin increased from 1983 to 2015,the annual average sunshine hours showed a downward trend.There is a big difference between the annual average sunshine hours of the river basin and the national average sunshinehours,which shows that the annual average sunshine hours of the Wujiang River Basin is not the product of the national background climate,but the climate effect of the watershed water area changes.(8)The water area of Puding County is larger than that of Longli County,and its monthly average temperature increase and seasonal average temperature decrease are smaller than that of Longli County;monthly average maximum temperature decrease and seasonal average maximum temperature decrease are larger than Longli County;The increase in monthly average minimum temperature islarger than that in Longli County,and the decrease in seasonal average minimum temperature is smaller than that in Longli County.This shows that the increase in water area can effectively regulatet he local temperature,reduce the temperature in the warm season and increase the temperature in the cold season.The average monthly precipitation increase in Puding County and the seasonal average precipitation decrease are larger than those in Longli County.The monthly average wind speed in Puding County is smaller than that in Longli County,and the seasonal average wind speed is larger than that in Longli County.The increase in monthly average relative humidity and seasonal average relative humidity in Puding County is larger than that in Longli County,which again shows that the water area has a humidifying effect.The monthly average sunshine hours in Puding County increased less than that in Longli County,and the decline in seasonal average sunshine hours was largerthan that in Longli County,indicating that the increase in water area will reduce the local sunshine hours. |
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