Figure 1. The profiles of θ, RH, q, N and the MLH) derived from these profiles.The h determined by individual standard (magenta dotted line) and h0 which integrates the information of θ, RH, q and N (black solid line) (a) Station #14898 at 00:00 UTC on August 13. 2006, (b) station #14898 at 00:00 UTC on August 23, 2006. Taken from Wang & Wang 2014
Background/Introduction
- The mixing layer is formed when discontinuous turbulence exists due to temperature inversions between the upper and lower layers of the atmosphere.
- The heights of the mixing layer are usually the highest during daytime periods (1,000-2,000m range) because of the strong solar heating and the lowest during the night.
- Studying the mixing layer height (MLH)) is a very important topic because it will help us understand the transport and dispersion processes of pollutants emitted from different sources in the troposphere that affect air pollution, weather and climate change.
- By identifying the turning point of the radiosonde profile, the MLH can be determined by many methods, such as potential temperature (θ ), relative humidity (RH), specific humidity (q) and atmospheric refractivity (N).
Research Objectives
- Making the best estimate for mixing layer height to help understand differences of air pollution in San Juan, PR and Sterling, Virginia.
- Observing the trends in the MLH for the dates of June 29. 2021 - July 6, 2021.
Rationale/Motivation for the Study
- Mixing layer height parameter for verification and validation in numerical weather prediction. Erroneous determination can impact forecasting.
- MLH is used in model evaluation of chemical transport models to estimate the pollution concentrations under various meteorological conditions and air quality episode analyses for air quality planning and management.
Methods
- Obtained radiosonde data from University of Wyoming’s Atmospheric Sounding website during June 29th, 2021 to July 6th, 2021 at 0 UTC and 12 UTC from San Juan, Puerto Rico and Sterling, Virginia.
- Developed algorithm in Python open, process and visualize rawinsonde data.
- Collected the 10 greatest gradient values for potential temperature and 10 least gradient values for relative humidity, specific humidity and refractivity at heights between 0 meters and 4,000 meters in altitude.
- Plotted the mixing layer height where at least three parameters had the same height when going in descending order for potential temperature and ascending order for relative humidity, specific humidity and refractivity.
- Observed the trends in mixing layer height over the course of the days studied.
This study is supported and monitored by The National Oceanic and Atmospheric Administration – Cooperative Science Center for Earth System Sciences and Remote Sensing Technologies under the Cooperative Agreement Grant #: NA16SEC4810008.
The authors would like to thank NOAA Educational Partnership Program with Minority Serving Institutions for fellowship support for Raisa Rodríguez, Rahim Kamra and NOAA Center for Earth System Sciences and Remote Sensing Technologies.
The statements contained within the poster are not the opinions of the funding agency or the U.S. government, but reflect the author’s opinions.
Results
- San Juan, PR at 0 UTC had mean MLH of 1936.7 m and standard deviation of 435.7 m and at 12 UTC had mean MLH of 1964.25 m and standard deviation of 335.09 m for days where MLH could be calculated. For Sterling, VA at 0 UTC had mean MLH of 1974.2 m and standard deviation of 1093.03 m and at 12 UTC had mean MLH of 1666.33 m and standard deviation of 1220.48 m, again, for days where MLH could be calculated
- San Juan, PR at 0 UTC had frequency of 6 while 12 UTC had frequency of 8. Sterling, VA at 0 UTC had frequency of 5 while 12 UTC had frequency of 6.
- A low mixing layer height would mean that it would be likely for a higher concentration of air pollution to exist near the ground, while a high mixing layer height would mean that it would be likely for a lower concentration of air pollution to exist near the ground.
Discussion
- According to a scientific article [3], many scientific researches have provided detailed information of weather conditions during heavy pollution periods but they certify that variations in atmospheric MLH are not well understood.
- As a key meteorological factor, the MLH has a strong effect on the occurrence, maintenance, and dissipation of heavy pollution.
References
- X. Y. Wang and K. C. Wang,. (2014). Estimation of atmospheric mixing layer height from radiosonde data. Atmos. Meas. Tech., 7, 1701–1709.
Rawinsonde Estimation of Mixing Layer Height
Raisa Rodríguez1,3,4 , Rahim Kamara1,2,5, Ruben Delgado3,6
1NOAA CESSRST Summer Bridge Scholar, 2NCAS-M, 3CESSRST, 4University of Puerto Rico-Mayaguez,
5University of Maryland, College Park, 6University of Maryland, Baltimore County
2021 Summer Research Symposium - August 9, 2021
Figure 2. Planetary boundary layer evolution. Taken from Caicedo et al. 2020.
Figure 3. Potential temperature profile and mixing layer height at Sterling, VA for June 30, 2021 at 0 UTC and 12 UTC
Figure 4. Mixing layer height versus days for San Juan, PR and Sterling, VA
Figure 4. Mixing layer height mean and standard deviation calculated for days between June 29, 2021 and July 6, 2021 for San Juan, PR and Sterling , VA