The phrase "dry subtropics" refers to a region that is located in the subtropical zone of the Earth and experiences a lack of rainfall or dry conditions. Full definition
And because higher temperatures also increase evaporation, other areas, such as the already dry subtropics, are likely to dry out further. (scientificamerican.com)
Also the circulation belts will expand poleward, causing the dry subtropics to expand. (planet3.org)
Writing in a 2011 literature review in the science journal Nature, the physicist Joe Romm elaborates on how increased heat and evaporation can lead to a vicious cycle: «Precipitation patterns are expected to shift, expanding the dry subtropics. (chimalaya.org)