Holbach, H. M., Uhlhorn, E. W., & Bourassa, M. A. (2018). Off-Nadir SFMR Brightness Temperature Measurements in High-Wind Conditions.
J. Atmos. Oceanic Technol., 35(9), 1865–1879.
Abstract: Wind and wave-breaking directions are investigated as potential sources of an asymmetry identified in off-nadir remotely sensed measurements of ocean surface brightness temperatures obtained by the Stepped Frequency Microwave Radiometer (SFMR) in high-wind conditions, including in tropical cyclones. Surface wind speed, which dynamically couples the atmosphere and ocean, can be inferred from SFMR ocean surface brightness temperature measurements using a radiative transfer model and an inversion algorithm. The accuracy of the ocean surface brightness temperature to wind speed calibration relies on accurate knowledge of the surface variables that are influencing the ocean surface brightness temperature. Previous studies have identified wind direction signals in horizontally polarized radiometer measurements in low to moderate (0�20 m s−1) wind conditions over a wide range of incidence angles. This study finds that the azimuthal asymmetry in the off-nadir SFMR brightness temperature measurements is also likely a function of wind direction and extends the results of these previous studies to high-wind conditions. The off-nadir measurements from the SFMR provide critical data for improving the understanding of the relationships between brightness temperature, surface wave�breaking direction, and surface wind vectors at various incidence angles, which is extremely useful for the development of geophysical model functions for instruments like the Hurricane Imaging Radiometer (HIRAD).
Zheng, Y., Ali, M. M., & Bourassa, M. A. (2016). Contribution of Monthly and Regional Rainfall to the Strength of Indian Summer Monsoon.
Mon. Wea. Rev., 144(9), 3037–3055.
Ahern, K., Bourassa, M. A., Hart, R. E., Zhang, J. A., & Rogers, R. F. (2019). Observed Kinematic and Thermodynamic Structure in the Hurricane Boundary Layer During Intensity Change.
Mon. Wea. Rev., .
Abstract: The axisymmetric structure of the inner-core hurricane boundary layer (BL) during intensification [IN; intensity tendency ≥ 20 kt (24 h)−1], weakening [WE; intensity tendency < −10 kt (24 h)−1], and steady-state [SS; the remainder] periods are analyzed using composites of GPS dropwindsondes from reconnaissance missions between 1998 and 2015. A total of 3,091 dropsondes were composited for analysis below 2.5 km elevation—1,086 during IN, 1,042 during WE, and 963 during SS. In non-intensifying hurricanes, the lowlevel tangential wind is greater outside the radius of maximum wind (RMW) than for intensifying hurricanes, implying higher inertial stability (I) at those radii for non-intensifying hurricanes. Differences in tangential wind structure (and I) between the groups also imply differences in secondary circulation. The IN radial inflow layer is of nearly equal or greater thickness than nonintensifying groups, and all groups show an inflow maximum just outside the RMW. Non-intensifying hurricanes have stronger inflow outside the eyewall region, likely associated with frictionally forced ascent out of the BL and enhanced subsidence into the BL at radii outside the RMW. Equivalent potential temperatures (θe) and conditional stability are highest inside the RMW of non-intensifying storms, which is potentially related to TC intensity. At greater radii, inflow layer θe is lowest in WE hurricanes, suggesting greater subsidence or more convective downdrafts at those radii compared to IN and SS hurricanes. Comparisons of prior observational and theoretical studies are highlighted, especially those relating BL structure to large-scale vortex structure, convection, and intensity.
Smith, S. R., Bourassa, M. A., & Sharp, R. J. (1999). Establishing More Truth in True Winds.
J. Atmos. Oceanic Technol., 16(7), 939–952.
Weissman, D. E., Bourassa, M. A., & Tongue, J. (2002). Effects of Rain Rate and Wind Magnitude on SeaWinds Scatterometer Wind Speed Errors.
J. Atmos. Oceanic Technol., 19(5), 738–746.
Hanley, D. E., Bourassa, M. A., O'Brien, J. J., Smith, S. R., & Spade, E. R. (2003). A Quantitative Evaluation of ENSO Indices.
J. Climate, 16(8), 1249–1258.
Bourassa, M. A., Vincent, D. G., & Wood, W. L. (1999). A Flux Parameterization Including the Effects of Capillary Waves and Sea State.
J. Atmos. Sci., 56(9), 1123–1139.
Sharp, R. J., Bourassa, M. A., & O'Brien, J. J. (2002). Early Detection of Tropical Cyclones Using Seawinds-Derived Vorticity.
Bull. Amer. Meteor. Soc., 83(6), 879–889.
Bourassa, M. A., Vincent, D. G., & Wood, W. L. (2001). A Sea State Parameterization with Nonarbitrary Wave Age Applicable to Low and Moderate Wind Speeds.
J. Phys. Oceanogr., 31(10), 2840–2851.
Pegion, P. J., Bourassa, M. A., Legler, D. M., & O'Brien, J. J. (2000). Objectively Derived Daily “Winds” from Satellite Scatterometer Data.
Mon. Wea. Rev., 128(9), 3150–3168.