Abstract
Tropical cyclones (TCs) are essential elements of the hydrological cycle in tropical and subtropical regions. In the present study, the contribution of TCs to seasonal precipitation around the tropical and subtropical North America is examined. When TC activity over the tropical eastern Pacific (TEP) or the Intra Americas Seas (IAS) is below (above-normal), regional precipitation may be below (above-normal). However, it is not only the number of TCs what may change seasonal precipitation, but the trajectory of the systems. TCs induce intense precipitation over continental regions if they are close enough to shorelines, for instance, if the TC center is located, on average, less than 500 km-distant from the coast. However, if TCs are more remote than this threshold distance, the chances of rain over continental regions decrease, particularly in arid and semi-arid regions. In addition, a distant TC may induce subsidence or produce moisture divergence that inhibits, at least for a few days, convective activity farther away than the threshold distance. An analysis of interannual variability in the TCs that produce precipitation over the tropical and subtropical North America shows that some regions in northern Mexico, which mostly depend on this effect to undergo wet years, may experience seasonal negative anomalies in precipitation if TCs trajectories are remote. Therefore, TCs (activity and trajectories) are important modulators of climate variability on various time scales, either by producing intense rainfall or by inhibiting convection at distant regions from their trajectory. The impact of such variations on water availability in northern Mexico may be relevant, since water availability in dams recovers under the effects of TC rainfall. Seasonal precipitation forecasts or climate change scenarios for these regions should take into account the effect of TCs, if regional adaptation strategies are implemented.
Highlights
Tropical cyclones (TCs) are frequently associated with disasters given the adverse impacts that the related intense winds, storm surges, and heavy rainfall have on vulnerable regions (Smith et al, 2009)
The contribution of TCs in seasonal precipitation over Mexico was explored by using the rain-gauge station daily data and adding the rainfall when TCs are present at a distance less than the critical threshold of 500 km from the location of the station
When TCs affect the southern part of the Baja California peninsula, precipitation may vary from 500 to 800 mm yr−1
Summary
Tropical cyclones (TCs) are frequently associated with disasters given the adverse impacts that the related intense winds, storm surges, and heavy rainfall have on vulnerable regions (Smith et al, 2009). Some studies have examined how TCs may result in a decrease of seasonal precipitation (e.g., Shanko and Chamberlain, 1998) having a dual effect: inducing large amounts of precipitation in few days, or reducing seasonal precipitation due to their absence or distant trajectories. In this way, negative regional seasonal precipitation anomalies and even meteorological droughts can occur in years of diminished TC activity or when the dominant TC trajectories are distant from continental regions by inducing enhanced moisture divergence (Shanko and Chamberlain, 1998). These changes in regional circulations and precipitation are not always documented as important factors of seasonal precipitation for water planning
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