Kirk L. Holub

The Amazon Dense GNSS Meteorological Network: A New Approach for Examining Water Vapor and Deep Convection Interactions in the Tropics

AbstractThe complex interactions between water vapor fields and deep atmospheric convection remain one of the outstanding problems in tropical meteorology. The lack of high spatial–temporal resolution, all-weather observations in the tropics has hampered progress. Numerical models have difficulties, for example, in representing the shallow-to-deep convective transition and the diurnal cycle of precipitation. Global Navigation Satellite System (GNSS) meteorology, which provides all-weather, high-frequency (5 min), precipitable water vapor estimates, can help. The Amazon Dense GNSS Meteorological Network experiment, the first of its kind in the tropics, was created with the aim of examining water vapor and deep convection relationships at the mesoscale. This innovative, Brazilian-led international experiment consisted of two mesoscale (100 km × 100 km) networks: 1) a 1-yr (April 2011–April 2012) campaign (20 GNSS meteorological sites) in and around Manaus and 2) a 6-week (June 2011) intensive campaign (15 G...

Water vapor and surface observations in northwestern Mexico during the 2004 NAME Enhanced Observing Period

[1] We report on precipitable water vapor (PWV) from a Global Positioning System (GPS) receiver and surface meteorological network during the 2004 North American Monsoon Experiment (NAME) in northwestern Mexico. The monsoon onset is evident as a large PWV increase over several days beginning July 1. Data in the Sierra Madre Occidental (SMO) foothills reveal a dynamical transition in mid-August from smaller, sub-synoptic scale to larger, synoptic scale moisture structure. During the Sub-synoptic phase in the SMO foothills, a positive feedback operates where near-daily precipitation supplied moisture maintains 15% higher surface mixing ratios that lower the lifting condensation level facilitating initiation of moist convection. Along the western edge of the SMO, precipitation typically occurs hours after the local temperature maximum, triggered by westward propagating convective disturbances. Precipitation is typically preceded by a rapid rise in PWV and sharp decrease in surface temperature, implying models must include moist convective downdrafts in the NAM area. Citation: Kursinski, E. R., R. A. Bennett, D. Gochis, S. I. Gutman, K. L. Holub, R. Mastaler, C. Minjarez Sosa, I. Minjarez Sosa, and T. van Hove (2008), Water vapor and surface observations in northwestern Mexico during the 2004 NAME Enhanced Observing Period, Geophys. Res. Lett., 35, L03815,

The North American Monsoon GPS Transect Experiment 2013

AbstractNorthwestern Mexico experiences large variations in water vapor on seasonal time scales in association with the North American monsoon, as well as during the monsoon associated with upper-tropospheric troughs, mesoscale convective systems, tropical easterly waves, and tropical cyclones. Together these events provide more than half of the annual rainfall to the region. A sufficient density of meteorological observations is required to properly observe, understand, and forecast the important processes contributing to the development of organized convection over northwestern Mexico. The stability of observations over long time periods is also of interest to monitor seasonal and longer-time-scale variability in the water cycle. For more than a decade, the U.S. Global Positioning System (GPS) has been used to obtain tropospheric precipitable water vapor (PWV) for applications in the atmospheric sciences. There is particular interest in establishing these systems where conventional operational meteorolo...