Variability in upwelling across the tropical tropopause and correlations with tracers in the lower stratosphere

Temporal variability of the upwelling near the tropical tropopause on daily to annual timescales is investigated using three different estimates computed from the ERA-Interim reanalysis. These include upwelling archived by the reanalysis, plus estimates derived from thermodynamic and momentum balance calculations. Substantial variability in upwelling is observed on both seasonal and sub-seasonal timescales, and the three estimates show reasonably good agreement. Tropical upwelling should exert strong influence on temperatures and on tracers with large vertical gradients in the lower stratosphere. We test this behavior by comparing the calculated upwelling estimates with observed temperatures in the tropical lower stratosphere, and with measurements of ozone and carbon monoxide (CO) from the Aura Microwave Limb Sounder (MLS) satellite instrument. Time series of temperature, ozone and CO are well correlated in the tropical lower stratosphere, and we quantify the influence of tropical upwelling on this joint variability. Strong coherent annual cycles observed in each quantity are found to reflect the seasonal cycle in upwelling. Statistically significant correlations between upwelling, temperatures and tracers are also found for sub-seasonal timescales, demonstrating the importance of upwelling in forcing transient variability in the lower tropical stratosphere

Thermal structure of intense convective clouds derived from GPS radio occultations

Thermal structure associated with deep convective clouds is investigated using Global Positioning System (GPS) radio occultation measurements. GPS data are insensitive to the presence of clouds, and provide high vertical resolution and high accuracy measurements to identify associated temperature behavior. Deep convective systems are identified using International Satellite Cloud Climatology Project (ISCCP) satellite data, and cloud tops are accurately measured using Cloud-Aerosol Lidar with Orthogonal Polarization (CALIPSO) lidar observations; we focus on 53 cases of near-coincident GPS occultations with CALIPSO profiles over deep convection. Results show a sharp spike in GPS bending angle highly correlated to the top of the clouds, corresponding to anomalously cold temperatures within the clouds. Above the clouds the temperatures return to background conditions, and there is a strong inversion at cloud top. For cloud tops below 14 km, the temperature lapse rate within the cloud often approaches a moist adiabat, consistent with rapid undiluted ascent within the convective systems

Feedlot and carcass traits of Bonsmara, Angus, and Brahman steers

Last updated: 6/12/200

Trajectory model simulations of ozone (O<sub>3</sub>) and carbon monoxide (CO) in the lower stratosphere

A domain-filling, forward trajectory model originally developed for simulating stratospheric water vapor is used to simulate ozone (O3) and carbon monoxide (CO) in the lower stratosphere. Trajectories are initialized in the upper troposphere, and the circulation is based on reanalysis wind fields. In addition, chemical production and loss rates along trajectories are included using calculations from the Whole Atmosphere Community Climate Model (WACCM). The trajectory model results show good overall agreement with satellite observations from the Aura Microwave Limb Sounder (MLS) and the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) in terms of spatial structure and seasonal variability. The trajectory model results also agree well with the Eulerian WACCM simulations. Analysis of the simulated tracers shows that seasonal variations in tropical upwelling exerts strong influence on O3 and CO in the tropical lower stratosphere, and the coupled seasonal cycles provide a useful test of the transport simulations. Interannual variations in the tracers are also closely coupled to changes in upwelling, and the trajectory model can accurately capture and explain observed changes during 2005–2011. This demonstrates the importance of variability in tropical upwelling in forcing chemical changes in the tropical lower stratosphere

Variability and trends in dynamical forcing of tropical lower stratospheric temperatures

The contribution of dynamical forcing to variations and trends in tropical lower stratospheric 70 hPa temperature for the period 1980–2011 is estimated based on ERA-Interim and Modern-Era Retrospective Analysis for Research and Applications (MERRA) reanalysis data. The dynamical forcing is estimated from the tropical mean residual upwelling calculated with the momentum balance equation, and with a simple proxy based on eddy heat fluxes averaged between 25° and 75° in both hemispheres. The thermodynamic energy equation with Newtonian cooling is used to relate the dynamical forcing to temperature. The deseasonalised, monthly mean time series of all four calculations are highly correlated (~ 0.85) with temperature for the period 1995–2011 when variations in radiatively active tracers are small. All four calculations provide additional support to previously noted prominent aspects of the temperature evolution 1980–2011: an anomalously strong dynamical cooling (~ −1 to −2 K) following the Pinatubo eruption that partially offsets the warming from enhanced aerosol, and a few years of enhanced dynamical cooling (~ −0.4 K) after October 2000 that contributes to the prominent drop in water entering the stratosphere at that time. The time series of dynamically forced temperature calculated with the same method are more highly correlated and have more similar trends than those from the same reanalysis but with different methods. For 1980–2011 (without volcanic periods), the eddy heat flux calculations give a dynamical cooling of ~ −0.1 to ~ −0.25 K decade−1 (magnitude sensitive to latitude belt considered and reanalysis), largely due to increasing high latitude eddy heat flux trends in September and December–January. The eddy heat flux trends also explain the seasonality of temperature trends very well, with maximum cooling in January–February. Trends derived from momentum balance calculations show near-zero annual mean dynamical cooling, with weaker seasonal trends especially in December–January. These contradictory results arising from uncertainties in data and methods are discussed and put in context to previous analyses

Equatorial Kelvin waves as revealed by EOS Microwave Limb Sounder observations and European Centre for Medium-Range Weather Forecasts analyses: Evidence for slow Kelvin waves of zonal wave number 3

[1] Temperature and ozone observations from the Microwave Limb Sounder (MLS) on the EOS Aura satellite are used to study equatorial wave activity in the autumn of 2005. In contrast to previous observations for the same season in other years, the temperature anomalies in the middle and lower tropical stratosphere are found to be characterized by a strong wave-like eastward progression with zonal wave number equal to 3. Extended empirical orthogonal function (EOF) analysis reveals that the wave 3 components detected in the temperature anomalies correspond to a slow Kelvin wave with a period of 8 days and a phase speed of 19 m/s. Fluctuations associated with this Kelvin wave mode are also apparent in ozone profiles. Moreover, as expected by linear theory, the ozone fluctuations observed in the lower stratosphere are in phase with the temperature perturbations, and peak around 20–30 hPa where the mean ozone mixing ratios have the steepest vertical gradient. A search for other Kelvin wave modes has also been made using both the MLS observations and the analyses from one experiment where MLS ozone profiles are assimilated into the European Centre for Medium-Range Weather Forecasts (ECMWF) data assimilation system via a 6-hourly 3D var scheme. Our results show that the characteristics of the wave activity detected in the ECMWF temperature and ozone analyses are in good agreement with MLS data

Steer Temperament Influences Stress Responsiveness to Handling Typical In BeefCattle Management

Last updated: 6/1/200