## 1 Introduction  
The global surface temperature has been increasing since the pre-industrial period [1, 2, 3]. It is undeniable that climate change has a notable impact on natural ecosystems and indirectly affects human life and the economy across the world [4]. Rangeland ecosystems, however, are usually second- or third-class quality land in terms of production potential and are therefore vulnerable to climate change. Worldwide, 40-50 million km\({}^{2}\) of rangelands constitute about 40% of the total land area [5] and have been chiefly used in fodder production. Moreover, rangelands play an essential role in regulating the carbon cycle of forests due to their contribution to a large part of regional, continental, and global net primary productivity (NPP). The climatic and multiple environmental attributes have been considered as an important factor driving the global terrestrial NPP in previous studies. For example, [PERSON] et al. [6] reported that climate change has resulted in increasing global terrestrial NPP during the period between 1982 to 1999. In contrast, climate change events like drought have resulted in a decline in global terrestrial NPP over the past decades according to [PERSON] and [PERSON] [7]. Thus, the influence of climate change on NPP has largely remained ambiguous owing to its complexity in nature [8; 9]. Whilst the influence of climate change on the variability of NPP has been studied extensively in Mongolia [10; 11], the impact of droughts either singly or in combination with other environmental factors, such as fires and land use change, on the Mongolian terrestrial NPP is inadequately explored. Mongolia has widespread drought-sensitive land, which merits the assessment of NPP response to droughts because half (52%) of the land area comprises arid and semiarid environments [12]. An earlier study revealed that drought affects one-fourth of the country every 2 to 3 years, while half of it is affected every 4 to 5 years [13]. More recent findings have shown that the average drought-affected areas accounted for one-third of the total area every year from 2000 to 2016 [14]. Thus, the impact of droughts in Mongolia is more severe than in other regions due to which it has been identified as one of the extremely vulnerable countries to climate change [15; 16]. Drought is one of the most common catastrophes induced by climate change throughout the world. Drought can be simply defined as long-term environment dryness usually resulting from a low precipitation at the specific location [17]. As both drought and aridity characterize environment dryness, some authors use the term drought and aridity/dryness interchangeably [18]. Unfortunately, its occurrence is predicted to increase in the context of increasing climatic variability in the future [19]. Drought inadvertently reduce vegetation productivity. Recently, the notable effects of drought events on NPP at both regional and global levels have been observed [7; 20; 21; 22]. Studies have shown that both observed and simulated droughts resulted in reduced NPP worldwide [22; 23]. However, some studies have shown that drought increased the NPP of the natural ecosystem [7; 24]. Moreover, some studies have found that productivity remained stable under long-term drought events [25]. Global-scale research based on Moderate Resolution Imaging Spectroradiometer (MODIS) imagery revealed that NPP decreased by 50% during 2000-2014 in Mongolia [22]. Although the MODIS NPP products (MOD17) at the annual scale are excellent at the global scale, they may contain systematic errors in arid and semiarid regions such as Mongolia because drought is a major disastrous event during the growing season for this country. Therefore, daily to seasonal scale modeling efforts need to be tested considering the independent contribution of drought on NPP across Mongolia. Moreover, the mechanism and magnitude of the impact of drought on terrestrial NPP variability at a local to regional scale have largely remained uncertain.