SMEX02: Field scale variability, time stability and similarity of soil moisture
SMEX02: Field scale variability, time stability and similarity of soil moisture
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DOI：
10.1016/j.rse.2004.02.017
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发表时间：
2004-09-30
影响因子：
13.5
通讯作者：
Miller, D
中科院分区：
文献类型：
--
作者：
Jacobs, JM;Mohanty, BP;Miller, D
对测量土壤湿度的航空或空间遥感器进行评价需要进行战略性的地面取样。作为2002年土壤水分试验（SMEX 02）的一部分，在爱荷华州的核桃溪流域的四个农田中，每天在90-140个地点进行表层土壤水分采样。土壤、植被和地形的各种组合构成了这片土地的特征。根据田间特征和土壤含水量，需要3-32次独立测量以获得田间平均土壤体积含水量，偏差为+/-2%，置信区间为95%。用平均每田14个样品对飞机微波仪器反演的土壤水分产品进行验证，对于干（土壤体积含水量< 10%）或湿（土壤体积含水量>25%）范围比中间土壤含水量范围更合适。时间稳定性分析表明，一个适当选择的单一采样点可以提供类似的精度在一系列的土壤水分条件。基于景观位置（洼地，山顶，陡坡，缓坡）的分析表明，缓坡的位置始终表现出时间稳定的功能。山顶和陡坡位置始终低估了平均田间土壤水分。土壤参数不能用于识别时间稳定的功能，因为采样位置相对较高的砂含量始终低估了现场平均值，而那些位置相对较高的粘土含量始终高估了现场平均值。然而，斜坡位置表征的时间稳定功能增强使用土壤属性。具有最佳时间稳定性特征的缓坡位置是与现场平均值（28-30%粘土）相比具有中等至中等高粘土含量的位置。(C)2004年爱思唯尔公司All rights reserved.
Evaluation of air- or space-bome remote sensors measuring soil moisture requires strategic ground-based sampling. As part of the Soil Moisture Experiment 2002 (SMEX02), daily surface soil moisture sampling at 90-140 locations were conducted in four fields in Walnut Creek watershed, Iowa. Various combinations of soils, vegetation, and topography characterize the fields. Depending on the field's characteristics and soil moisture content, 3-32 independent measurements were necessary to capture the field mean volumetric soil moisture with a +/-2% bias and 95% confidence interval. Validation of the retrieved soil moisture products from the aircraft microwave instruments using the average of 14 samples per field is more appropriate for dry (< 10% volumetric soil moisture) or wet (>25% volumetric soil moisture) range than for intermediate soil moisture range. Time stability analysis showed that an appropriately selected single sampling point could provide similar accuracy across a range of soil moisture conditions. Analyses based on landscape position (depression, hilltop, steep slope, and mild slope) showed that locations with mild slopes consistently exhibit time stable features. Hilltop and steep slope locations consistently underestimated mean field soil moisture. Soils parameters could not be used to identify time stable features as sampling locations with relatively high sand content consistently underestimated the field mean while those locations with relatively high clay content consistently overestimated the field mean. However, the slope position characterization of time stable features was enhanced using soils properties. The mild slope locations having the best time-stable features are those with moderate to moderately high clay content as compare to the field average (28-30% clay). (C) 2004 Elsevier Inc. All rights reserved.