Search Results

You are looking at 1 - 2 of 2 items for :

  • Author or Editor: Jerald A. Brotzge x
  • Journal of Hydrometeorology x
  • Refine by Access: All Content x
Clear All Modify Search
Jerald A. Brotzge

Abstract

Few surface-observation networks exist that provide comprehensive multiyear, multiseason observations of surface energy fluxes and subsurface soil moisture and temperature, combined with near-surface atmospheric data. More such networks are needed to validate, improve, and calibrate current global weather and climate models, including those used as the backbone or background models in global reanalysis. One such measurement system is the Oklahoma Mesonet–Oklahoma Atmospheric Surface-layer Instrumentation System (OASIS), which provides atmospheric, surface, and soil data in real time. This study compares 2 yr of surface energy and water budget data from two OASIS sites located in two distinct climate zones with NCEP–NCAR global reanalysis (GR) estimates. The intraseasonal hydrological and thermodynamic cycles are discussed. Results show generally good agreement between most reanalysis values and observations. Incoming and reflected shortwave radiation are largely overestimated by the GR, and incoming longwave radiation is slightly underestimated by the GR when compared to OASIS observations. The GR significantly overestimates latent heat (LE) at the Idabel, Oklahoma (IDAB) site. Furthermore, the GR likely underestimates entrainment of drier air from above the PBL and mixes the turbulent fluxes over too shallow of a layer. Both the reanalysis and observations find a positive water residual for the easternmost site (IDAB) but estimate a negative near-surface water residual for the western site [Boise City, Oklahoma (BOIS)]. Overall, surface fluxes and thermodynamic properties were well analyzed by the reanalysis at capturing the unique features associated with each OASIS site.

Full access
Jerald A. Brotzge and Kenneth C. Crawford

Abstract

A reliable method for monitoring the surface energy budget is critical to the development and validation of numerical models and remote sensing algorithms. Unfortunately, closure of the energy budget remains difficult to achieve among measurement systems. Reasons for nonclosure still are not clearly understood, and, until recently, few long-term datasets were available to address this issue of nonclosure. This contribution examined 108 days of a year dataset collected from collocated eddy correlation (EC) and Bowen ratio (BR) systems. Differences between systems were examined across seasonal and diurnal cycles to better understand nonclosure of the energy budget. Closure by the EC system was observed to vary with season and with time of day, primarily as a function of latent heat flux. Furthermore, the EC and BR methods partitioned energy differently, with the EC system favoring latent heat flux and the BR system favoring sensible heat flux.

Instrument error, surface heterogeneity, and the theoretical assumptions behind the EC and BR methods are discussed to explain observed patterns in closure and the differences between measurement systems. Sensor error and variability in net radiation and soil moisture data increased uncertainty in measurements of net radiation and ground heat flux. Significant differences in soil temperature and flux between sites appear to be caused by the heterogeneity of vegetation and soil type. Finally, several assumptions of the BR method are examined to explain observed differences in sensible and latent heat flux between systems. Recommendations for future observational studies are proposed.

Full access