hello

there are plenty of Aridity indexes.

Kopponen, Martone, Emberger, Kimura, etc.

If you want them to increase with increasing aridity you can reverse the ratios, or use 1/x.

regards

ARIDITY INDEX is an indicator characterizing the degree of dryness (aridity) of the climate. According to Thornthwaite, it is equal to 100 d / n, where d is the lack of moisture (the sum of monthly differences between precipitation and total evaporation for three months, when the precipitation rate is less than the annual evaporation); n is the sum of monthly values ​​of evaporation for the indicated months.

According to De Marton, for this area, the ratio R / (t + 10), where R is the annual precipitation in centimeters and t is the average annual temperature in degrees Celsius. The formula can also be applied to individual months by replacing annual amounts with monthly ones.

According to Stenz, the quotient of evaporation (E) by the amount of precipitation (R).

Regards, Pushkin Sergey Viktorovich

Because it is precipitation to evapotranspiration ratio, so it will be lowest in the hottest places

aridity index= No of rainy days*Mean precipitation/ day

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Mean temperature+10

Search Results

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Variation of Aridity Index and the Role of Climate ... - MDPI

www.mdpi.com › pdf

PDFSep 28, 2017 - 3. Methods. 3.1. Calculation of Aridity Index. AI = ET0. Pre. (2) where ET0 is the annual potential evapotranspiration (mm) and Pre is the annual precipitation (mm). The ET0 can be estimated by Penman-Monteith method [18] as follows: ET0 = 0.408A(Rn − G) + γby Y Li - ‎2017

Dear Shivam,

Have a look at this recent and important article which explains the aridity index nicely:

Article The Grass Is Not Always Greener on the Other Side: Seasonal ...

Thanks

Thank you for sharing your knowledge

Aridity Index (AI) is a numerical indicator which is used for measuring the degree of dryness of climate of a place. It is opposite to humidity index. It is calculated as the ratio of P/PET, where P is the average annual precipitation and PET is the potential evapotranspiration (UNEP, 1992).

Here is the important link to calculate Aridity Index. Please check this link

Article An aridity index defined by precipitation and specific humidity

Thank you Ankur Srivastava . I have read your reference, they have explained very nicely.

Most people associate the term aridity with drylands, which evokes various types of images, including sparse vegetation (e.g. succulents and other xerophytic plants), sand dunes, small amounts of water, little or no surface water, scant rainfall and high temperatures. This is only partly true as aridity is, in fact, a climate phenomenon principally characterised by a shortage of water and therefore, aridity also occurs in cold climates where precipitation falls mainly as snow, e.g. in the Arctic and Antarctica (the “polar deserts”), because they receive little net precipitation each year. Water is, of course, the key to understanding aridity but at the same time has a physical meaning on the ground as determined by climate, vegetation and soil processes. Hence, aridity is commonly quantified by comparing the long-term average of water supply or precipitation (P) to the long-term average of climatic water demand (known as potential evapotranspiration). Potential evapotranspiration (PET) is a measure of the “drying power” of the atmosphere to remove water from land surfaces by evaporation (e.g. from the soil and plant canopy) and via plant transpiration. Consequently, if PET is greater than P, then the climate is considered to be arid. Of course, anomaly water deficits may also occur over shorter time periods, e.g. seasonally or monthly, which are called droughts depending on their intensity and duration. The term aridity is meteorologically related to water availability, with many different techniques proposed to precisely define it. The Aridity Index (AI) is a simple but convenient numerical indicator of aridity based on long-term climatic water deficits and is calculated as the ratio P/PET. The AI is a widely used measure of dryness of the climate at a given location. Using the AI, six subtypes of arid lands or drylands are classified: cold, hyper-arid, arid, semi-arid, dry subhumid and humid.