Rainfall totals houston11/10/2023 ![]() ![]() Area soil moisture content between 20 has been reduced by an average rate of 2.3 cm annually due to recent dry conditions (Famiglietti and Rodell 2013). The coefficients of variation for Houston and Atlanta, the standard deviation of annual rainfall totals from 1970 to 2012 divided by the mean, is 0.26 and 0.17, respectively. of precipitation during the calendar year (Johnston 2007) in the past 30 years, Intercontinental Airport’s (IAH) rain gauge has been below this level three times (NCDC 2012). In 2007, as Atlanta was reeling from a severe drought, that city received nearly 32 in. While Houston and Atlanta share similar average precipitation profiles, with each city receiving its 50-inch total at relatively uniform rates throughout the year, larger variations in annual totals are more prevalent in Houston. Unlike other southeastern cities, year-to-year rainfall totals can vary heavily. of rain annually, with 5-inch decreases in average totals occurring over east-to-west partitions that are 20 miles wide (NOAA, AHPS 2014) (Fig. According to the National Weather Service’s Advanced Hydrologic Prediction Service, the metropolitan area of Houston receives approximately 50 in. In Southeast Texas, precipitation patterns are heavily influenced by mesoscale events associated with the Gulf of Mexico (Ohashi and Kida 2002), and average rainfall increases dramatically moving from the Northwest towards the Southeast. This suggests that the area is drying even with steady or increasing amounts of rain. Even though rainfall has not decreased, average relative humidity has fallen. An examination of hourly data does not show an increase in extreme rainfall events or a decrease in the number of hours during which rain has fallen. While some stations show larger amounts of rain falling during fewer days, these trends do not hold across all periods. ![]() While recent decades may have seen more rain relative to earlier periods, a combined analysis of observation stations across different parts of the Region shows that long-term trends are dependent on when the data is selected relative to a drought cycle. The analyses answered several questions: Have global and regional climate change models predicted precipitation increases in Southeast Texas and are future increases expected? Do historical monthly precipitation totals at various sites in the region provide clear trends of wetter conditions that can be discerned from long-term drought cycles? Are rainfall patterns changing with less frequent, heavier rain events? Do the reported increases in annual rainfall actually lead to wetter conditions in the region? Climate models have not predicted larger annual average precipitation totals nor do they forecast increases for Southeast Texas. In order to determine if the additional rainfall has been influenced by warming temperatures or is within the variability of the State’s long-term drought cycles, several analyses were performed on historical climate data. The Region has seen an increase in its reported normal annual precipitation totals in recent decades. Southeast Texas houses a precipitation transition zone between drier conditions to the North and West and some of the wettest parts of the continental U.S. ![]()
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