Kumar, V., Jana, S., Bhardwaj, A., Deepa, R., Sahu, S. K., Pradhan, P. K., et al. (2018). Greenhouse Gas Emission, Rainfall and Crop Production Over North-Western India. TOECOLJ , 11 (1), 47–61.
Abstract: Background:
LaCasce, J. H., Escartin, J., Chassignet, E. P., & Xu, X. (2018). Jet instability over smooth, corrugated and realistic bathymetry. J. Phys. Oceanogr. , .
Abstract: The stability of a horizontally- and vertically-sheared surface jet is examined, with a focus on the vertical structure of the resultant eddies. Over a flat bottom, the instability is mixed baroclinic/barotropic, producing strong eddies at depth which are characteristically shifted downstream relative to the surface eddies. Baroclinic instability is suppressed over a large slope for retrograde jets (with a flow anti-parallel to topographic wave propagation), and to a lesser extent for prograde jets (with flow parallel to topographic wave propagation), as seen previously. In such cases, barotropic (lateral) instability dominates if the jet is sufficiently narrow. This yields surface eddies whose size is independent of the slope but proportional to the jet width. Deep eddies still form, forced by interfacial motion associated with the surface eddies, but they are weaker than under baroclinic instability and are vertically aligned with the surface eddies. A sinusoidal ridge acts similarly, suppressing baroclinic instability and favoring lateral instability in the upper layer.
Laurencin, C., & Misra, V. (2018). Characterizing the Variations of the motion of the North Atlantic tropical cyclones. Meteorol Atmos Phys , 130 (303), 1–12.
Abstract: In this study, we examine the seasonal and interannual variability of the North Atlantic (NATL) tropical cyclone (TC) motion from the historical Hurricane Database (HURDAT2) over the period 1988-2014. We characterize these motions based on their position, lifecycle, and seasonal cycle. The main findings of this study include: (1) of the 11,469 NATL TC fixes examined between 1988 and 2014, 81% of them had a translation speed of < 20 mph; (2) TCs in the deep tropics of the NATL are invariably slow-moving in comparison with TCs in higher latitudes. Although fast-moving TCs (> 40 mph) are exclusively found north of 30 N, the slow-moving TCs have a wide range of latitude. This is largely a consequence of the background steering flow being weaker (stronger) in the tropical (higher) latitudes with a minimum around the subtropical latitudes of NATL; (3) there is an overall decrease in the frequency of all categories of translation speed of TCs in warm relative to cold El Niño Southern Oscillation (ENSO) years. However, in terms of the percentage change, TCs with a translation speed in the range of 10-20 mph display the most change (42%) in warm relative to cold ENSO years; and (4) there is an overall decrease in frequency across all categories of TC translation speed in small relative to large Atlantic Warm Pool years, but in terms of percentage change in the frequency of TCs, there is a significant and comparable change in the frequency over a wider range of translation speeds than the ENSO composites. This last finding suggests that Atlantic Warm Pool variations have a more profound impact on the translation speed of Atlantic TCs than ENSO.
Laxenaire, R., Speich, S., & Alexandre S. (2019). Evolution of the thermohaline structure of one Agulhas Ring reconstructed from satellite altimetry and Argo floats. Journal of Geophysical Research. Oceans , 124 (12), 8969–9003.
Le Sommer, J., Chassignet, E. P., & Wallcraft, A. J. (2018). Ocean Circulation Modeling for Operational Oceanography: Current Status and Future Challenges. In and J. Verron J. Tintoré A. Pascual E. P. Chassignet (Ed.), New Frontiers in Operational Oceanography (pp. 289–305). Tallahassee, FL: GODAE OceanView.
Abstract: This chapter focuses on ocean circulation models used in operational oceanography, physical oceanography and climate science. Ocean circulation models area particular branch of ocean numerical modeling that focuses on the representation of ocean physical properties over spatial scales ranging from the global scale to less than a kilometer and time scales ranging from hours to decades. As such, they are an essential build-ing block for operational oceanography systems and their design receives a lot of attention from operational and research centers.
Lee, C. M., Starkweather, S., Eicken, H., Timmermans, M. - L., Wilkinson, J., Sandven, S., et al. (2019). A Framework for the Development, Design and Implementation of a Sustained Arctic Ocean Observing System. Front. Mar. Sci. , 6 .
Liu, M., Lin, J., Wang, Y., Sun, Y., Zheng, B., Shao, J., et al. (2018). Spatiotemporal variability of NO2 and PM2.5 over Eastern China: observational and model analyses with a novel statistical method. Atmos. Chem. Phys. , 18 (17), 12933–12952.
Abstract: Eastern China (27-41 degrees N, 110-123 degrees E) is heavily polluted by nitrogen dioxide (NO2), particulate matter with aerodynamic diameter below 2.5 mu m (PM2.5), and other air pollutants. These pollutants vary on a variety of temporal and spatial scales, with many temporal scales that are nonperiodic and nonstationary, challenging proper quantitative characterization and visualization. This study uses a newly compiled EOF-EEMD analysis visualization package to evaluate the spatiotemporal variability of ground-level NO2, PM2.5, and their associations with meteorological processes over Eastern China in fall-winter 2013. Applying the package to observed hourly pollutant data reveals a primary spatial pattern representing Eastern China synchronous variation in time, which is dominated by diurnal variability with a much weaker day-to-day signal. A secondary spatial mode, representing north-south opposing changes in time with no constant period, is characterized by wind-related dilution or a buildup of pollutants from one day to another.
Liu, Q., Tan, Z. - M., Sun, J., Hou, Y., Fu, C., & Wu, Z. (2020). Changing rapid weather variability increases influenza epidemic risk in a warming climate. Environmental Research Letters , 15 (4).
Abstract: The continuing change of the Earth's climate is believed to affect the influenza viral activity and transmission in the coming decades. However, a consensus of the severity of the risk of influenza epidemic in a warming climate has not been reached. It was previously reported that the warmer winter can reduce influenza epidemic-caused mortality, but this relation cannot explain the deadly influenza epidemic in many countries over northern mid-latitudes in the winter of 2017-2018, one of the warmest winters in recent decades. Here we reveal that the widely spread 2017-2018 influenza epidemic can be attributed to the abnormally strong rapid weather variability. We demonstrate, from historical data, that the large rapid weather variability in autumn can precondition the deadly influenza epidemic in the subsequent months in highly populated northern mid-latitudes; and the influenza epidemic season of 2017-2018 was a typical case. We further show that climate model projections reach a consensus that the rapid weather variability in autumn will continue to strengthen in some regions of northern mid-latitudes in a warming climate, implying that the risk of influenza epidemic may increase 20% to 50% in some highly populated regions in later 21st century.
Liu, Y., Tan, Z. - M., & Wu, Z. (2019). Noninstantaneous Wave-CISK for the Interaction between Convective Heating and Low-Level Moisture Convergence in the Tropics. J. Atmos. Sci. , 76 (7), 2083–2101.
Abstract: The interaction between tropical convective heating and thermally forced circulation is investigated using a global dry primitive-equation model with the parameterization of wave-conditional instability of the second kind (CISK). It is demonstrated that deep convective heating can hardly sustain itself through the moisture convergence at low levels regardless of the fraction of immediate consumption of converged moisture. In contrast, when the fraction is large, shallow convective heating and its forced circulation exhibit preferred growth of small scales. As the “CISK catastrophe” mainly comes from the instantaneous characters of moisture-convection feedback in the conventional wave-CISK, a noninstantaneous wave-CISK is proposed, which highlights the accumulation-consumption (AC) time scale for the convective heating accumulation and/or the converged moisture consumption. In the new wave-CISK, once moisture is converged, the release of latent heat takes place gradually within an AC time scale. In this sense, convective heating is not only related to the instantaneous moisture convergence at the current time, but also to that which occurred in the past period of the AC time scale. The noninstantaneous wave-CISK could guarantee the occurrence of convective heating and/or moisture convergence at larger scales, and then favor the growth of long waves, and thus solve the problem of CISK catastrophe. With the new wave-CISK and AC time scale of 2 days, the simulated convective heating-driven system bears a large similarity to that of the observed convectively coupled Kelvin wave.
Luecke, C. A., Arbic, B. K., Bassette, S. L., Richman, J. G., Shriver, J. F., Alford, M. H., et al. (2017). The Global Mesoscale Eddy Available Potential Energy Field in Models and Observations: GLOBAL LOW-FREQUENCY EDDY APE. J. Geophys. Res. Oceans , 122 (11), 9126–9143.
Abstract: Global maps of the mesoscale eddy available potential energy (EAPE) field at a depth of 500 m are created using potential density anomalies in a high‐resolution 1/12.5° global ocean model. Maps made from both a free‐running simulation and a data‐assimilative reanalysis of the HYbrid Coordinate Ocean Model (HYCOM) are compared with maps made by other researchers from density anomalies in Argo profiles. The HYCOM and Argo maps display similar features, especially in the dominance of western boundary currents. The reanalysis maps match the Argo maps more closely, demonstrating the added value of data assimilation. Global averages of the simulation, reanalysis, and Argo EAPE all agree to within about 10%. The model and Argo EAPE fields are compared to EAPE computed from temperature anomalies in a data set of “moored historical observations” (MHO) in conjunction with buoyancy frequencies computed from a global climatology. The MHO data set allows for an estimate of the EAPE in high‐frequency motions that is aliased into the Argo EAPE values. At MHO locations, 15–32% of the EAPE in the Argo estimates is due to aliased motions having periods of 10 days or less. Spatial averages of EAPE in HYCOM, Argo, and MHO data agree to within 50% at MHO locations, with both model estimates lying within error bars observations. Analysis of the EAPE field in an idealized model, in conjunction with published theory, suggests that much of the scatter seen in comparisons of different EAPE estimates is to be expected given the chaotic, unpredictable nature of mesoscale eddies.
