An aridity index defined by precipitation and specific humidity

SummaryThe United Nations Environmental Programme (UNEP), defined an aridity index (AI) by the ratio of the annual precipitation and potential evapotranspiration (PET) totals. In this work, specific humidity was used instead of PET and a new aridity index (Iq) has been defined using the ratio of annual precipitation totals and annual mean specific humidity (Sh). As shown in this study, Sh can be easily computed with very high accuracy (3.569% error rate) with mean temperature, relative humidity and local pressure which are most commonly and widely measured meteorological data. The single point correlation graph of Sh which shows the entrance of aridity through the South Eastern Anatolia Region into Turkey and the distribution of the aridity over Turkey explains the relationship with Sh and aridity. According to the common and different aspects of arid zones found with AI, Iq and Erinç aridity index (Im), Iq found to be applicable for monitoring climate change and distribution of arid zones.

► A new aridity index was defined.
► The relationship with specific humidity (Sh) and aridity was showed.
► The Iq index can be calculated with the most readily available variables.
► It was shown that there is no drawback in using the computed Sh.
► Iq index can be used for monitoring climate change and the distribution of aridity.