Analysing regional climate forcing on historical precipitation variability in Northeast Puerto Rico

Abstract

The tropical forests of northeast Puerto Rico (NE PR) and the Luquillo Mountains (LM) are a large repository for biodiversity and have an important role in regional biogeochemical processes. Precipitation is a key driver of the productivity of these sensitive ecosystems. This study analyses historical precipitation variability from 1985 to 2014 at El Verde Field Station (EVFS) at 380 m on the north facing slope of the LM. The primary objective of this study is to identify atmospheric states that lead to extreme wet/dry conditions at EVFS. This study also investigates how those wet/dry atmospheric states change over the study period through an epoch approach on annual and seasonal timescales. Self‐organizing maps (SOMs) are used to produce atmospheric states from ERA‐Interim low‐tropospheric moisture and circulation variables. These atmospheric states are downscaled to precipitation at the EVFS rain gauge. A probability density function of observed precipitation is calculated for each atmospheric state. Changes in node frequency, which is the number of days mapping to a particular node compared to the total number of days in the temporal period, are used to evaluate changes in wet/dry atmospheric states at EVFS. Results indicate that low‐precipitation days at EVFS are associated with atmospheric states with high 1000–700 hPa bulk wind shear and decreased 700 hPa moisture. Wet days in the study region are associated with moist low‐tropospheric environments with low wind shear. Our results indicate an increased frequency of dry season atmospheric states with lower 700 hPa moisture. Over the study period, the dry season has a decrease in median and extreme precipitation during rainy days (days >0 mm). A decrease in early rainfall season median precipitation on rainy days is observed despite an increase in days with measurable precipitation, likely driven by an increase in light rainfall days (<5 mm).

An Empirical Study of the Relationship between Seasonal Precipitation and Thermodynamic Environment in Puerto Rico

“…For instance, there is essentially no relationship between the GDI and 3-km ET/precipitation during the LRS. Further, the GDI contains no kinematic component, but previous research (Ramseyer and Mote 2018) suggests that the environment's kinematic character also exercises an important control on more shallow and isolated tropical convection. Future research may consider modifying the GDI to include a kinematic component as well as evaluating the ability of coarse-resolution model output, such as the CFSv2, to forecast seasonal GDI values several months in advance.…”

Historical trends in the trade wind inversion in the tropical North Atlantic Ocean and Caribbean

“…The direct and indirect aerosol effects associated with the SAL, arising from its high mineral dust concentration, can lead to drought and precipitation reductions across the TNA, even as far as the Caribbean (Mote et al ., 2017; Ramseyer et al ., 2019). Recent Caribbean hydroclimate studies have shown that precipitation and drought strongly respond to moisture changes in the mid‐troposphere (~850–700 hPa) and wind shear through the low‐ and mid‐troposphere (Ramseyer and Mote, 2016, 2018).…”

Alaska Daily Extreme Precipitation Processes in a Subset of CMIP5 Global Climate Models

“…Self‐organizing maps (SOMs; Hewitson & Crane, ; Kohonen, ; Sheridan & Lee, ) have been used in the past to analyze the impact of large‐scale circulation on synoptic‐scale processes; they then can be used to develop a synoptic climatology of the large‐scale circulation patterns associated with extreme events (e.g., Cassano et al, ). As a result, previous studies have used SOMs to analyze the variability in extreme events within several different geographic regions (e.g., Agel et al, ; Alexander et al, ; Cavazos, , ; Horton et al, ; Lee et al, ; Ramseyer & Mote, ). Within Alaska, Glisan et al () used SOMs to study topographically forced widespread precipitation extremes, and they found this type of analysis tool to be effective.…”