Font Size: a A A

The Variation Of Precipitation And Evolution Features Of Precipitable Water Vapor During Heavy Rain In The Urumqi Summer

Posted on:2013-04-28Degree:MasterType:Thesis
Country:ChinaCandidate:S J WangFull Text:PDF
GTID:2230330362970218Subject:Physical geography
Abstract/Summary:PDF Full Text Request
The variation of precipitation and evolution features of precipitable water vaporduring heavy rain in the Urumqi summer are analyed.The following conclusions are:1. The diurnal variation of hourly precipitation and rainfall frequency areconsistent. The peaks of hourly precipitation and rainfall frequency are both from20:00to11:00, and the minimum value occurred at16:00. The frequency of rainfallless than or equal to1.0mm/h was the most, the frequency of rainfall great than orequal to1.1mm/h but less than or equal to3.0mm/h was less than1.0mm/h, but thecontribution of great than or equal to1.1mm/h but less than or equal to3.0mm/h wasthe biggest to precipitation.2. Different magnitudes of precipitation intensity have some difference amongdifferent years. The frequency of light rain was the most, the second were moderaterain and heavy rain, and the least was torrential rain. Light rain, moderate rain andheavy rain were easiest to occur at the first half of the night, and torrential rain waseasiest to occur at afternoon. Light rain was easiest to occur was in the middle of July,moderate rain was easiest to occur in the middle of May, and heavy rain was easiestto occur in mid-to-late May. The early and middle of May, middle of July, and lateAugust were the period of time which torrential rain was easiest to occur.3. The peaks of rainfall events with duration of1-3hours occur at the first halfof the night, and duration of4-6hours and7-9hours often appear at night, whilelong duration rainfall events often appear in the afternoon and after midnight. Thetotal rain days of20years in Urumqi have some difference among different years,but the interannual change was unconspicuous. Compare the second decade with thefirst decade, rain days of other magnitudes have decreased, and yet the torrential raindays have increased.4. The evolution features of GPS-PWV during10times heavy rain processes areanalyzed. It shows that it always appears evidently wetting process about one to threedays and water vapor jumps once or twice before precipitation began. TheGPS-PWV during rainfall almost is about twice of climatic value, its abrupt variationcorresponds with begin and end of precipitation. So GPS-PWV can exhibit a clearindex of water vapor evolution during rainfall in arid for short range weatherforecast.5. The related coefficient of temperature, relative humidity, water vapor density and precipitable water vapor between radiometer and radiosonde are0.9929,0.7376,0.9222and0.9440, the result predicted has no significant difference at1%level. Theprofile result at all seasons show that the temperatures measured by radiometer aresmaller than that measured by radiosonde, but the relative humidity and water vapordensity measured by radiometer are larger than that measured by radiosonde, and twodetection methods have exist system error. The humiture measured by ground-basedradiometer is affected by weather, and effect is obvious on relative humidity andprecipitable water vapor, temperature and water vapor densit are influenced muchless. The average bias measured by radiometer and radiosonde have differences indifferent height and seasons. The related coefficient of63%precipitable water vaporbetween radiometer and radiosonde in each month are above0.9. The relatedcoefficient of each season is above0.8except winter. The minimum and maximumbiases of precipitable water vapor are found in winter and summer.6. The temperature and humidity observation data measured by ground-basedradiometer during rainfall processes are analyzed. It shows that temperature andwater vapor density have rapid increase in every hight level close to precipitation,and decease rapidly when precipitation began. The Variation Feature of PWV andILW have very good corresponding relation during rainfall processes, and also have agood indication role to begin of precipitation.
Keywords/Search Tags:Urumqi, diurnal variation, rain intensity, precipitable water vapor, ground-based radiometer, temperature, water vapor density
PDF Full Text Request
Related items