新疆塔城地区大风年际振荡及环流背景

Interannual oscillation and circulation features of gale weather in Tachang Prefecture,Xinjiang

运用线性趋势法、小波分析等方法,对塔城地区1961-2008年大风实测资料进行分析,得出以下结论:(1)塔城地区年均大风日数为31 d,地区中部有一条呈东北-西南走向的大风多发区,老风口一带存在着年均大风日数>100 d的大风频发区;(2)除塔城、老风口站东南、偏东大风频率最高外,其余各站均以偏西,西北大风最多;(3)近48 a塔城地区大风日数以-9.97 d/10a的速率显著减少,各站大风日数也均表现为显著减少的趋势,大风日数较多的区域大风日数减少速率也较快;(4)塔城地区大风日数在18 a左右、7~8 a、2~3 a的时间尺度上振荡周期最为显著;(5)影响新疆的冷空气强度和频率有所减弱(减少),是塔城地区大风日数显著减少的主要原因。

Based on meteorological date of 10 observational stations from 1961 to 2008 in Tacheng Prefecture,Xinjiang,China,with climatological statistics methods of linear trend analysis and Morlet wave analysis,the data of windy weather have been analyzed in detail to get comprehensive understanding of the spatial-temporal distribution of gale days.Some significant results and new facts are obtained as follows:(1)the annual mean number of gale days is selected as the major index to divide into four sub-regions,which are fewer gale region(where annual gale weather are less than 10 days),more gale region(where annual gale weather are between 10 days and 50 days),much more gale region(where annual gale weather are between 50 days and 100 days) and frequent region(where annual gale weather are more 100 days).As for the spatial distribution,annual mean gale days are 31 days in this area.Most parts of Tacheng area are more gale region,the frequent region of windy weather sites at Laofengkou zone which annual gale days are more than 100 days(annual mean gale days of Laofengkou station is 144 days from 2001 to 2005),but Wusu station is the fewer gale region which annual gale days are mere 7 days.The much more gale region mainly locates in the middle of Tacheng area from northeast to southwest.It has close relationship between gale days spatial distribution and special geographic environment which gorges,mountains districts have more gale weathers than other districts.(2)As for the frequency of gale,there existed significant regional differences,there are mainly southeaster and east wind in Laofengkou station,taking up 61.8%.A further analysis indicated that windy weather depended on the special geographic environment and atmospheric circulation pattern,in addition to the development and persistence of surface Mongolia high directly impacts on the seasonal variation of gale days.(3)Seasonally,the windy weather mainly occur in spring,accounting for 34.2%,secondly in autumn,and the least in winter over Tacheng area,whereas the gale weather of Laofengkou zone were the most in winter,taking up 37.8 %,the next is in spring,taking up 28.4%.(4)In the whole area,the generally varying trend of the annual mean gale days is obviously reducing at rate of-9.97 d/10 a during 1961-2008,which the significant level reached to 0.01,ecpecial Yumin station located Tacheng-Emin Basin with decreasing trend at rate of-18.3 d/10 a.(5)Considering decadal variation,the feature on frequency of windy weather in recent 48 a are as follows: a fluctuating increase during 1960s,a high frequency period in the mid-1960s,then the variation of gale days is obviously decreasing during 1970s and 1980s,the mumber of gale days remain steady after 1990s.(6)Morlet wave analysis showed that there have obvious oscillation period of 18 a,meanwhile there still exist period of 7-8 a,2-3 a,respectively.(7)The cold air activities is reducing in intensity and less in frequency recent several decade in Xinjiang Province,which may be primary causes for the decreasing number of gales.Above results are significant to further understand changing and distribution of windy weather in the past 48 a and to find out forming mechanism.Meanwhile,the results could be helpful to tap and utilize climatic resource and improve the local ecology and environments.