## Materials and Methods  
### Moisture Content and Transport in the Global Atmosphere  
Earth's climate system is made up of five basic parts: the atmosphere, hydrosphere, cryosphere, lithosphere, and biosphere, which interact with each other evolving over time and responding to internal and external perturbations. All the water on the earth form the hydrosphere which is commonly called \"the water shell of our planet.\" Estimates indicate that the aggregated volume of water on earth is around \(1.38\times 10^{9}\) km\({}^{3}\)[65; 66]. The prevailing portion of this, \(\sim\)\(1.34\times 10^{9}\) km\({}^{3}\) (about 97% of the total volume), is in the oceans. Oceans form the largest water reservoir on earth. The second largest global water reservoir includes ice sheets, sea ice, and glaciers containing a total of about \(23\times 10^{6}\) km\({}^{3}\) (\(\sim\)1.7% of total planetary volume of water) followed by groundwater (\(\sim\)\(18\times 10^{6}\) km\({}^{3}\) of water or \(\sim\)1.3% of the total volume). Apart from that, much smaller volumes of water are contained in lakes, rivers, and streams (\(\sim\)\(18\times 10^{4}\) km\({}^{3}\) of water or \(\sim\)0.013% of the total volume) and in the atmosphere (\(\sim\)\(13\times 10^{3}\) km\({}^{3}\) of water or \(\sim\)0.00094% of the total volume) [65; 66]. In the atmosphere, the volumetric water vapor content varies almost from zero to 4%, and considerably changes across the globe and is subject to seasonal influence. The content of water vapor reaches its maximum at the earth's surface and decreases rapidly with height. For example, at an altitude of 5 km, the water vapor content is nearly ten times less than that of the earth's surface, and at an altitude of 8 km--one hundred times less. Thus, above 10-15 km, the content of water vapor in the air is negligible [67]. Despite the fact that the amount of water contained in the atmosphere is much less than the total available water on earth, it would be very difficult to overestimate the key role of atmospheric water vapor in forming the energy balance of our planet and global hydrological cycle [68; 69; 70]. Water vapor along with carbon dioxide, methane, and ozone, forms the group of the major atmospheric GHGs [1]. Most likely that if there were no GHGs in the earth atmosphere, then our planet would hardly have been inhabited by humans. In fact, the water vapor is the most crucial natural GHG that is responsible for more than 60% of the total earth's greenhouse effect [71]. The positive feedback of water vapor in climate system is well-known; an increase in the atmospheric temperature caused by other factors increases water evaporations from oceans, lakes, rivers, and soil leading to rising concentrations of water vapor in the atmosphere and consequently increasing the greenhouse effect [1]. On the other hand, growing moisture content in the atmosphere contributes to the formation of cloud cover, which, in turn, reflects shortwave solar radiation, thereby increasing the planetary albedo. This leads to an anti-greenhouse effect [72]. Thus, the effect of atmospheric moisture on climate processes is complex and of varied nature. In analyzing the global distribution and transport of moisture in the atmosphere, the balance equation can be written as [73]:  
\[\frac{\partial W}{\partial t}+\
abla\cdot\mathbf{Q}=E-P \tag{1}\]Here \(W\) is the amount of precipitable water within the atmospheric column extending above the earth's surface of unit area, \(\mathbf{Q}\) is the vertically integrated horizontal moisture flux, \(E\) is the rate of evaporation, and \(P\) is the rate of precipitation from the atmospheric column.