Carbon Cycle

My primary research is investigating the carbon cycle through the satellite observations and model simulations. The research involves retrieving CO2 from satellites, analyzing the CO2 variability, and simulating and inversing CO2 surface sources/sinks with the chemistry and transport models. We generated the first global map of mid-tropospheric CO2 from AIRS instrument and found that the CO2 concentrations are not distributed uniformly in the mid-troposphere for the first time. I also work on retrieving CO2 profiles from OCO-2, which can help to better understand the vertical structure for CO2 over the global domain. In addition to retrieve CO2 from satellites, I also investigated the atmospheric variability of CO2 and controlling processes. We identify the influences of Semi-Annual Oscillation, El Nino-Southern Oscillation, South Atlantic Walker circulation, Stratospheric Sudden Warming, Annular Mode, and drought on the mid-tropospheric CO2 for the first time [Jiang et al., 2010, 2012a, 2012b; 2013a; 2013b; 2015; 2016; 2017]. I am also interested in using chemistry and transport models to simulate and inverse possible sources and sinks of CO2 at surface. Some of my studies on the simulation of CO2 and its associated climate changes have already been published on important journals [Jiang et al., 2007; 2008; 2010; 2012a; 2012b; 2013a; 2013b; 2015; 2016; 2017].

I am also interested in investigating hydrological cycle and energy cycle through the satellite data and general circulation models. Based on the latest data sets of precipitation and water vapor from satellites, we have found that precipitation increased ~ 3.0% per decade and decreased ~ 4.7% per decade in the high-precipitation area and low-precipitation area, respectively. The opposite trends of precipitation between the high-precipitation and low-precipitation areas imply that extreme weather patterns intensified in response to global warming [Li et al., 2011]. Our recent paper [Kao et al., 2018] suggests that the current atmospheric models can quantitatively capture the characteristics of recycling rate from the observation. It was also found that the global warming due to the historic increase of the greenhouse gases can influence the temporal variations of precipitation over the wet and dry areas [Trammell et al., 2015; Kao et al., 2017]. In addition to the hydrological cycle, we explored the Lorenz energy cycle using three independent meteorological data sets. It was found that the efficiency of Earth's atmosphere as a heat engine increased in response to climate change. This result was published in Nature Communications in 2017 [Pan et al., 2017].

Ozone recovery is difficult to detect since total column ozone exhibits strong interannual variability (IAV) associated with dynamical processes and climate change. A primary motivation for studying the IAV of column ozone is to separate the anthropogenic perturbations of the ozone layer from natural variability. The distribution of ozone in the atmosphere is determined by a combination of photochemistry and transport. I have already investigated the pattern of observed changes in the ozone layer and their associated climate changes, using statistical methods outlined in my papers [Ruzmaikin et al., 2004; 2005; Jiang et al., 2004; 2005; 2008a; 2008b]. Using a chemistry-transport model, I carried out the first realistic simulation of the quasi-biennial oscillation (QBO) and the beat between QBO and the annual cycle (QBO-AB) signal in the column ozone from 1979 to 2002 [Jiang et al., 2004]. In addition, I used an idealized model and successfully revealed the characteristic pattern of the downward propagation of QBO and upward propagation of QBO-AB [Jiang et al., 2005]. The model results are similar to those exhibited in the Merged Ozone Data. Jiang et al. [2008a, 2008b] successfully investigated the interannual variability of column ozone in the high latitudes. We also found that 3-D GEOS Chemistry-Climate Model can simulate the impact of El Nino-Southern Oscillation on ozone reasonably well [Wang et al., 2011]. In the future, I will continue to use 3-D chemistry and transport models to study the interannual variability of ozone in the polar region, with emphasis on the influence of solar variability and the feedback of ozone on the radiation and meridional circulation. I am also interested in utilizing the global and regional air quality models (e.g., GEOS-Chem, RAQMS, and CMAQ) to investigate the air quality.

In addition to the terrestrial atmosphere, I am also interested in the atmosphere on other planets and moons. By combining observations of cloud and atmospheric temperature taken by two instruments on the Cassini spacecraft, we found for the first time that there is a significant temporal variation in the strength of the high-altitude equatorial jet on Saturn, which was published on Nature Geosciences [Li et al., 2011]. We finished the first global analysis of the atmospheric vortices on Saturn using observations from the Cassini spacecraft [Trammell et al., 2014]. We also used the long-term Cassini observations to conduct the first investigation of the temporal variation of Saturn's vortex dynamics from 2008 to 2015 [Trammell et al., 2016]. With the new discovery, scientists are getting a new picture of the general circulations on Saturn. The comparative studies of atmospheric systems between Earth and other astronomical bodies provide a wide perspective to better understand climate change on Earth.