Research
Dissertation Research Topic: Quantifying the Impact of Convection on the Temperature Structure in the Tropical and Midlatitudinal Upper Troposphere and Lower Stratosphere
Summary: The role convection plays in regulating and modifying temperatures in the troposphere has long been recognized. The lack of coincident measurements of storm convection with atmospheric thermodynamic structure, however, inhibits a clear understanding of such complex dynamic processes. This research quantifies the atmospheric temperature changes in the upper troposphere and lower stratosphere (UTLS) due to convection over the tropics and midlatitudes. Satellite measurements of storms from TRMM (Tropical Rainfall Measuring Mission) and GPM (Global Precipitation Measurement) are analyzed to categorize the convection by size, depth and convective intensity. The near-coincident high resolution temperature soundings from GPS radio occultation measurements along with ERA-Interim global reanalysis are used to quantify the impact of convection. The spatial differences between the tropics and midlatitudes are compared, while the latitude bands are broken down into smaller regions based on storm frequency and characteristics to quantify major changes on a region-to-region basis. The temporal variation of the UTLS convective temperature structure is evaluated on a seasonal and diurnal scale. Finally, gravity waves will be investigated to determine if there is a connection to the temperature changes seen in the UTLS after convection by calculating gravity wave activity using GPS radio occultation. This study will advance understanding of the complex physical processes involving storm evolution and their direct/indirect impact on temperatures and troposphere-stratosphere exchange.
Other Research
Analyzing GPS Radio Occultation Bending Angle and Refractivity Errors
Summary: Over the subtropical eastern oceans, strong subsidence in the free troposphere along with cool sea surface temperatures often results in a shallow stratocumulus cloud-topped atmospheric boundary layer (ABL). GPS radio occultation (RO) could provide the high vertical resolution thermodynamic structure in order to determine boundary layer characteristics. However, the sharp moisture gradient beneath the strong temperature inversion leads to a large refractivity gradient and often causes ducting across the ABL top. As a result, the ducting causes systematically negative biases in the RO refractivity (i.e., N-bias) inside the ABL. COSMIC GPS RO profiles are collocated with ERA-Interim reanalysis to quantify the N-bias in the moist lower troposphere in the stratocumulus regions. The negative N-bias in COSMIC soundings mainly lies below ~2 km, with the major contribution from ducting. Moreover, significant negative bending angle biases are present below ~2 km, with the maximum as large as -10% at about 0.8 km above surface. Such bending errors will introduce additional negative refractivity bias to the already large N-bias caused by ducting.
Summary: The role convection plays in regulating and modifying temperatures in the troposphere has long been recognized. The lack of coincident measurements of storm convection with atmospheric thermodynamic structure, however, inhibits a clear understanding of such complex dynamic processes. This research quantifies the atmospheric temperature changes in the upper troposphere and lower stratosphere (UTLS) due to convection over the tropics and midlatitudes. Satellite measurements of storms from TRMM (Tropical Rainfall Measuring Mission) and GPM (Global Precipitation Measurement) are analyzed to categorize the convection by size, depth and convective intensity. The near-coincident high resolution temperature soundings from GPS radio occultation measurements along with ERA-Interim global reanalysis are used to quantify the impact of convection. The spatial differences between the tropics and midlatitudes are compared, while the latitude bands are broken down into smaller regions based on storm frequency and characteristics to quantify major changes on a region-to-region basis. The temporal variation of the UTLS convective temperature structure is evaluated on a seasonal and diurnal scale. Finally, gravity waves will be investigated to determine if there is a connection to the temperature changes seen in the UTLS after convection by calculating gravity wave activity using GPS radio occultation. This study will advance understanding of the complex physical processes involving storm evolution and their direct/indirect impact on temperatures and troposphere-stratosphere exchange.
Other Research
Analyzing GPS Radio Occultation Bending Angle and Refractivity Errors
Summary: Over the subtropical eastern oceans, strong subsidence in the free troposphere along with cool sea surface temperatures often results in a shallow stratocumulus cloud-topped atmospheric boundary layer (ABL). GPS radio occultation (RO) could provide the high vertical resolution thermodynamic structure in order to determine boundary layer characteristics. However, the sharp moisture gradient beneath the strong temperature inversion leads to a large refractivity gradient and often causes ducting across the ABL top. As a result, the ducting causes systematically negative biases in the RO refractivity (i.e., N-bias) inside the ABL. COSMIC GPS RO profiles are collocated with ERA-Interim reanalysis to quantify the N-bias in the moist lower troposphere in the stratocumulus regions. The negative N-bias in COSMIC soundings mainly lies below ~2 km, with the major contribution from ducting. Moreover, significant negative bending angle biases are present below ~2 km, with the maximum as large as -10% at about 0.8 km above surface. Such bending errors will introduce additional negative refractivity bias to the already large N-bias caused by ducting.