The NOAA CPO Modeling, Analysis, Prediction, and Projections (MAPP) and Earth System Science (ESS) programs will host a webinar on the topic of climate extremes and efforts to better understand and predict them on Tuesday, April 8. During this webinar, speakers will touch on tropical cyclones, tornadoes, and drought, focusing on improved scientific understanding of these phenomena and their variability in a climate context as well as efforts to better simulate and predict them on various time scales. This work is directly relevant to the NOAA Societal Challenge “Reducing the Nation’s Vulnerability to Extreme Weather and Climate.” The announcement is provided below; you are invited to remotely join the session.
Kingtse Mo -- Two Types of Flash Drought over the United States -- Flash drought characterized by a sudden onset of high temperatures and reductions of soil moisture was investigated using the gridded station precipitation, surface temperature data and soil moisture (SM) and evapotranspiration (ET) from the North American Data Assimilation Systems. The study period is 1979-2011.
There are two types of flash drought. The type 1 flash drought prefers to occur in the areas that have dense vegetation cover in spring and summer. These are temperature driven events. The establishment of anti- cyclone centered over the North Central or the Northeast enhances heat waves. High temperature increases transpiration from vegetation and the increase of ET reduces SM. The heat waves persist only 1 to 2 pentads, but negative SM anomalies persist from one month to one season. The type 1 flash drought occurs most often in the crop-growing season and has high impact on agricultural products.
The type 2 flash drought is more common and can occur over areas east of 110oW with maxima over the Great Plains where the correlations between P and Tsurf are strong negative. The atmospheric circulation anomalies support dry conditions. The lack of rain reduces SM and decreases ET. The reductions of ET are balanced by the increases of sensible heat. That leads to heat waves. In this case, heat waves are caused by meteorological drought. This type of flash drought persists longer than the type 1 flash drought.
Chris Thorncroft -- Variability of African Easterly Waves and their relationship with Atlantic Tropical Cyclones -- Atlantic tropical cyclone variability varies substantially on intraseasonal-to-interannual timescales. This talk will show how variations in AEW structure and AEW-activity may play a role in determining this variability. The talk will first highlight how AEW structures can vary and influence the probability of downstream cyclogenesis on synoptic timescales. This will be followed by a consideration of how AEW-activity varies on intraseasonal timescales and the extent to which this can be an important influence on tropical cyclone variability. The significant roles played by the MJO and convectively coupled Kelvin waves will be emphasized.
Gabe Vecchi -- Towards Seasonal Prediction of Regional Tropical Cyclone Activity and Hydroclimate -- We explore results from GFDL-FLOR, a new high-resolution (50km atmospheric/land resolution) global coupled climate model, targetted to the understanding, intraseasonal-to-decadal prediction and near-term projection of regional and extreme climate. The high-resolution model produces skillful simulation and prediction of tropical cyclone activity. Initialized predictions of global hurricane activity show skill on regional scales, including in the Caribbean and Gulf of Mexico, comparable to the skill on basin-wide scales, suggesting that regional seasonal TC predictions may be a feasible target. We find that mean-state errors are a key constraint on the simulation and prediction of variations of regional climate and extremes, and methodologies for overcoming model biases are explored. Improvements in predictions of regional climate are due both to improved representation of local processes, and to improvements in the representation of large-scale climate and variability from improved process representation.
Scott Weaver -- Climatic Role of North American Low-Level Jets on U.S. Regional Tornadic Activity -- Variability of springtime tornadic activity over the U.S. is assessed through the connectivity of preferred modes of North American low-level jet (NALLJ) variability. The link between regional tornado activity and NALLJ variability as diagnosed from a consistent reanalysis system (i.e., NCEP/NCAR) serves as dynamical corroboration in light of an inhomogeneous tornado database. The analysis reveals a multidecadal variation in the strength of the NALLJ-tornado connection, especially over the southern Great Plains. Locally, this is a result of a southward shift of NALLJ variability modes during recent decades. Given the importance of NALLJ variability to the severe weather environment, seasonal predictability of NALLJ modes is further assessed in the NCEP Climate Forecast System Version 2.
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