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Mapping threats to agriculture in East Africa: Performance of MODIS derived LST for frost identification in Kenya’s tea plantations
International Journal of Applied Earth Observation and Geoinformation ( IF 7.5 ) Pub Date : 2018-06-19 , DOI: 10.1016/j.jag.2018.05.009
Susan M. Kotikot , Africa Flores , Robert E. Griffin , Absae Sedah , James Nyaga , Robinson Mugo , Ashutosh Limaye , Daniel E. Irwin

Frost is a major threat to crop productivity in the Kenyan highlands. With agriculture being central to the Kenyan economy, every effort needs to be taken to alleviate losses especially on high value crops like tea, the leading foreign exchange earner. Current frost mapping efforts by SERVIR, a joint initiative between National Aeronautics and Space Administration (NASA) and the U.S. Agency for International Development (USAID), and its hub institution in Eastern and Southern Africa, the Regional Center for Mapping of Resources for Development (RCMRD), utilizes Moderate Resolution Imaging Spectroradiometer (MODIS) derived Land Surface Temperature (LST) to probabilistically map areas that have been affected by frost. In this paper, we assessed the accuracy of these frost maps by testing the performance of MYD11A1 MODIS product in indicating areas affected by frost. MODIS derived LST values corresponding to frost and no frost observation locations and dates were reclassified according to 6 predetermined categories representing frost severity levels. The overall accuracy of each threshold category as LST cutoff separating frost and no frost affected areas was determined. An overall performance measure was then estimated using a Receiver Operating Characteristics curve (ROC). Overall accuracies of 67.3%–71.9% among the thresholds were obtained. An area under the ROC curve of 0.69 was obtained, indicating a poor performance of MODIS LST to distinguish frost from no frost areas. This shows that although MODIS derived LST can be used to identify frost-affected areas, it is not on its own sufficient in discriminating these areas with high levels of accuracy. Revision of temperature thresholds is recommended, in addition to improved characterization of frost occurrence in the region to include other factors that may be affecting frost occurrence. These results stand to better prepare the agricultural sector for damaging weather-related events.



中文翻译:

绘制对东非农业的威胁图:MODIS衍生的LST在肯尼亚茶园中鉴定霜冻的性能

霜冻是肯尼亚高地农作物生产力的主要威胁。由于农业对肯尼亚经济至关重要,因此需要采取一切措施来减轻损失,特别是在主要的外汇创收者茶等高价值作物上。美国国家航空航天局(NASA)与美国国际开发署(USAID)联合发起的SERVIR及其在东部和南部非洲的枢纽机构,区域资源图谱开发中心(SERVIR)当前进行的霜测图工作( RCMRD)利用中等分辨率成像光谱仪(MODIS)得出的陆地表面温度(LST)概率性地绘制了受霜冻影响的区域。在本文中,我们通过测试MYD11A1 MODIS产品在指示受霜影响的区域中的性能来评估这些霜图的准确性。根据代表霜冻严重程度的6个预定类别,将MODIS得出的对应于霜冻的LST值和无霜冻观测位置和日期进行了重新分类。确定了每个阈值类别的整体精度,即将霜冻和没有霜冻影响的区域分开的LST截止值。然后,使用接收器工作特性曲线(ROC)评估整体性能指标。阈值中的总体准确度为67.3%–71.9%。ROC曲线下的面积为0.69,表明MODIS LST区分霜和无霜区的性能较差。这表明尽管MODIS衍生的LST可用于识别受霜冻影响的区域,仅凭其自身能力还不足以高准确度地区分这些区域。除了改善该地区霜冻的特征外,还建议修改温度阈值,以包括可能影响霜冻发生的其他因素。这些结果将更好地为农业部门做好应对与天气有关的破坏性事件的准备。

更新日期:2018-06-19
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