西藏山南地区主要农区霜冻发生规律及防御对策

Occurrence Laws and Prevention Countermeasures of Frost in Main Agricultural Areas of Shannan Region in Tibet

利用山南地区主要农区气象观测站近30年(1980～2007年)历年霜期日数和逐日最低气温,详细分析了霜冻的时空分布特征以及突变情况,结果表明,沿江一线农区霜冻出现机率最高的是4月份,南部为5月份;年霜冻出现频率正在呈减少趋势;重霜冻每10年减少了1～3d;轻霜冻每10年减少了1～4d;沿江农区霜冻日数减少的突变是发生在20世纪90年代中期,具体发生在1997年左右,南部农区霜冻日数减少的突变发生在21世纪初,具体是在2006年左右。初霜冻主要出现在9月中旬至10月中旬近1个月的时间内;终霜冻主要出现在5月中旬至6月中旬近1个月的时间内,呈现自东向西和自北向南逐渐偏晚的特点;山南地区主要农区无霜期具有沿江一线长,南部农区短的特点。从空间分布来看,山南南部农区是霜冻高发区;沿江一线自西向东逐渐减少。

Using the frost days and daily frost temperature at the meteorological observing stations of main agricultural areas of Shannan Region from 1980 to 2007, the spatial - temporal distribution characteristics and abrupt change situations of frost were analyzed in detail. The results showed that frost mainly occurred in April in the main agricultural areas along the River and in May in southern area. The annual occurrence frequency of frost was decreasing. The days of heavy frost decreased 1 - 3 days every ten years and the days of slight frost decreased 1 -4 day every ten years. The abrupt change of frost days decrease in areas along the river occurred in the middle 1990s, about in 1997. The abrupt change of frost days decrease in southern areas occurred in early 21^st century, about in 2006. The initial frost days mainly occurred from middle September to middle October ; The final frost days mainly occurred from early May to early June, showing the characteristics of later and later from east to west and front north to south, The frost-free period in main agricultural areas was long in areas along the River and short in south areas. From the viewpoint of spatial distribution, the southern agricultural areas of Shannan Region were high-incidence areas of Shannan and that decreased from west to east along the river.