Drought is a complicated and costly natural hazard and identification of critical drought factors is critical for modeling and forecasting of droughts and hence development of drought mitigation measures (the Standardized Precipitation-Evapotranspiration Index) in both space and time. Here we quantified relationships between drought and 23 drought factors using remote sensing data during the period of 2002-2016. Based on the Gradient Boosting Algorithm (GBM), we found that precipitation and soil moisture had relatively large contributions to droughts. During the growing season, the relative importance of Normalized Difference Water Index (NDWI-7) for SPEI3, SPEI6, SPEI9, and SPEI12 reached as high as 50%. However, during the non-growing season, the Snow Cover Fraction (SCF) had larger fractional relative importance for short-term droughts in the Inner Mongolia and the Loess Plateau which can reach as high as 10%. We also compared Extremely Randomized Trees (ERT), H2O based Deep Learning (Model developed by H2O.deep learning in R H2O.DL), and Extreme Learning Machine (ELM) for drought prediction at various time scales, and found that the ERT model had the highest prediction performance with R-2 > 0.72. Based on the Meta-Gaussian model, we quantified the probability of maize yield reduction in the North China Plain under different compound dry-hot conditions. Due to extreme drought and hot conditions, Shandong Province in North China had the highest probability of >80% of the maize yield reduction; due to the extreme hot conditions, Jiangsu Province in East China had the largest probability of >86% of the maize yield reduction. (C) 2021 Elsevier B.V. All rights reserved.

Under conditions of ongoing climate warming and increasing anthropogenic impact on land resources, the use of moisture-saving soil-protecting technologies becomes especially important. Snow cover is of great importance for agriculture, as it changes radiation and thermal balance of underlying surface, protecting soil from cooling and winter crops from freezing, accumulates winter precipitation, being the most important source of increasing soil moisture reserves in arid and subarid zones in spring. Winter precipitation accounts for up to 30% of the annual norm. Soil moisture reserves formed with their help take up to 42% in total water consumption for grain crop yield formation during wet summer and up to 75% during dry summer. This article aims to study the effect of different methods of snow retention and snow cover height on the yield of grain crops. An effective method of snow retention is leaving high stubble after harvesting winter and spring crops. Leaving stubble bushes with a height of 0.35-0.40 m and a width of 1.5 m every 4.5 m provides accumulation of a solid snow cover in steppe areas with a height of 0.30-0.35 m, which increases the yield of wheat. Waders provide a more uniform distribution of snow cover than forest strips. Climate change contributes to the fact that snow retention becomes an urgent problem not only in the dry steppe, but also to the north - even in the forest-steppe. Creation of snow retarders was done on Vetelny state farm, located in Balashovsky district in the western part of Saratov region, in the steppe zone, where chernozem soils prevail in the soil cover. In the autumn period, snow barriers were installed, and in the winter period, their effect on snow accumulation was studied. The study of the effect of snow barriers on soil moisture accumulation during the growing season of winter wheat was compared in the zones of dry steppe, steppe and forest-steppe. It was revealed that during regrowth of winter wheat the least amount of productive moisture stocks in 0-1.0 m soil layer was contained in dry steppe 1377 m(3).ha(-1), the highest in forest-steppe zone up to 1841 m(3).ha(-1). Snow retention increased the amount of moisture in the soil in the dry steppe, steppe and foreststeppe zone by 251, 151, 115-131 m(3).ha(-1), or 18, 10, 6-8%, respectively. Thus, rational use of winter precipitation is a significant reserve of agricultural landscape productivity increase, especially in dry-steppe areas.