奥卡万戈河流域地区 NDVI、河流流量和气候的关系,International Journal of Climatology

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奥卡万戈河流域地区 NDVI、河流流量和气候的关系
International Journal of Climatology ( IF 3.5 ) Pub Date : 2021-06-24 , DOI: 10.1002/joc.7267
O. Moses _{1,

2} , R. C. Blamey ₁ , C. J. C. Reason ₁

Affiliation

奥卡万戈河流域（ORB）是南部非洲一个高度敏感和生物多样性的地区，其气候、植被和河流流量特征尚不清楚。本研究调查了该地区降雨、温度、归一化植被指数 (NDVI) 和河流流量之间的关系及其趋势和年际变化。研究发现，NDVI的空间格局与降雨的空间格局密切相关，但在月度和季节时间尺度上与温度的相关性较小。NDVI 与降雨量/温度之间的关系在 18.9°S 以北不同，降雨量高于其南部。通常，NDVI 与降雨量或温度之间存在 1-2 个月的滞后。还，该地区有大片地区在所有季节都显示出明显的变暖趋势以及湿润（主要在北部）。地表温度的这种上升趋势可能会加剧该地区严重干旱和火灾等极端事件的影响。还存在明显的年际变率，与厄尔尼诺-南方涛动 (ENSO)、副热带南印度洋偶极子和博茨瓦纳高压的降雨和温度以及 NDVI 与 ENSO 具有显着相关性。对于南方环形模式，仅在 12 月和 4 月发现了与降雨和温度的显着相关性。在更长的时间尺度上，相对于 1999-2005 年 10 月至 12 月干燥得多的 1999 年至 2005 年时期，重点也放在了 2006 年至 2013 年的潮湿时期。

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Relationships between NDVI, river discharge and climate in the Okavango River Basin region

The Okavango River Basin (ORB) is a highly sensitive and biodiverse region in southern Africa whose climate, vegetation and river discharge characteristics are not well understood. This study investigated relationships between rainfall, temperature, Normalized Difference Vegetation Index (NDVI) and river discharge over the region as well as their trends and interannual variability. It is found that spatial patterns of NDVI are closely related to those of rainfall, but less so with temperature at monthly and seasonal time scales. The relationships between NDVI and rainfall/temperature differ north of 18.9°S where rainfall is higher than to its south. Typically, there are lags of 1–2-months between NDVI and either rainfall or temperature. Also, there are large areas across the region that show significant warming trends in all seasons as well as wetting (mainly in the north). This increasing trend in surface temperature may act to worsen the impacts of extreme events such as severe drought and fire in the region. There is also pronounced interannual variability with significant correlations found with El Niño-Southern Oscillation (ENSO), the subtropical South Indian Ocean Dipole and the Botswana High for rainfall and temperature, and for NDVI with ENSO. For the Southern Annular Mode, significant correlations were found with rainfall and temperature only in December and April. On longer time scales, focus was also placed on the wet 2006–2013 period relative to much drier 1999–2005 epoch for October–December. The wetter conditions during 2006–2013 appear related to La Niña Modoki conditions and warmer sea surface temperature near Angola as well as regional circulation differences.

更新日期：2021-06-24

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