西藏青稞主要种植区干旱时空分布及致灾危险性评估

Spatiotemporal distribution of drought and hazard assessment of highland barley in Tibet

西藏青稞主要种植区是西藏地区主要粮食作物的产区,在气候变化和人类活动加剧的背景下,该区的农业深受干旱影响。根据《气象干旱等级》(GB/T 20481-2017)国家标准,计算西藏青稞主要种植区25个气象站点全生育期的逐日气象干旱综合指数(MCI),统计1981—2020年各站点的气象干旱过程,并进一步分析了西藏青稞主要种植区各生育期气象干旱的时空变化特征及致灾危险性等级分布。结果表明:(1)近40 a来西藏青稞主要种植区呈现气温显著上升(P<0.01),降水不显著增多的特点;季节性的气温和降水变化趋势差异明显。(2)干旱覆盖范围和持续日数总体呈现不同程度的下降趋势,干旱强度(除播种-分蘖期外)均有所增强;分蘖-抽穗期干旱最严重,1981—1990年干旱最重,2001—2010年干旱最轻。(3)各生育期干旱发生频率的高值区主要集中在日喀则市东部、拉萨市南部、昌都市西南部和山南市中部地区,低值区位于林芝市中部。(4)经验正交函数法(EOF)分析的各生育期主要模态有中部与中西部相反、全区一致、西南与东北相反。(5)各生育期干旱致灾危险性等级总体呈现西高东低的分布特征,其中,分蘖-抽穗期致灾危险性总体较高,抽穗-成熟期次之,播种-分蘖期最低。

In Tibet,highland barley is mostly cultivated on the primary crop-producing area in Tibet,China.However,drought resulting from climate change and intense human activities agriculture is considerably affecting agriculture in this area.The daily meteorological drought comprehensive index(MCI)of the growth period of 25 meteorological stations in the main growing areas of highland barley in Tibet,was calculated according to the national standard of“Meteorological Drought Grade”(GB/T 20481-2017),and the spatial and temporal variation characteristics of meteorological drought and the distribution of disaster risk were analyzed in the main growing areas of highland barley in Tibet.The results revealed that:(1)In the last 40 years,the air temperature in the main growing areas of highland barley in Tibet increased significantly(P<0.01),whereas the precipitation did not increase significantly.The seasonal variation trend of temperature and precipitation differed considerably.(2)The coverage and duration of drought exhibited a decreasing trend of various degrees,and the drought intensity(except sowing-tillering stage)enhanced.Drought was the most severe at the tillering-heading stage and in 1981—1990,whereas drought was the least severe in 2001—2010.(3)The high-value areas of drought frequency in various growth stages were in eastern Xigaze,southern Lhasa,southwestern Qamdo,and central Shannan,whereas low-value areas were in central Nyingchi.(4)The patterns of empirical orthogonal function analysis in various growth stages were opposite in central and central-western regions and consistent in the whole region,and opposite in southwest and northeast regions.(5)The drought disaster risk grades of each growth period were higher in the west and lower in the east.The disaster risk grades of the tillering-heading stage were generally higher,that of the heading-maturity stage was lower,and that of the sowing-tillering stage was the lowest.