Presentations

Climate model bias in equatorial Atlantic and possible reasons Monday, July 12, 2021:
climate_model_bias_in_equatorial_atlantic_and_possible_reasons.pdf

AGCMs suffer from biases of a reversed zonal gradient in SST and weak surface easterlies (the westerly bias) in the equatorial Atlantic during boreal spring. The first root is insufficient lower-tropospheric diabatic heating over Amazonia. The second root is erroneously weak zonal momentum flux (entrainment) across the top of the boundary layer.

Some Preliminary Evaluations of CCSM4 Model in Drought Forecast Monday, June 21, 2021
Danning Fu has shown some preliminary results of seasonal forecasts of the US drought by using an NMME model – CCSM4 model. Results indicate great challenges in ongoing pursuit of reliable forecasts of the US drought using dynamic models.
Causal Effect Networks Tuesday, April 13, 2021
Abstract:  This pdf file shows the methodology and application of a statistical method - causal effect networks (CEN), which is similar to the PCMCI approach. One paper has been reviewed regarding the Arctic drivers of midlatitude winter circulations. This method is also applied to understand the causality of Atlantic Niños.
Presentation: Precipitation Comparison for the East Asian Monsoon (Mingxin) Tuesday, February 23, 2021:
comparison_cmip56.pptx

This paper evaluated and compared the simulation of summer precipitation in China and the East Asian summer monsoon (EASM) by eight climate models from Phase 6 of the Coupled Model Intercomparison Project (CMIP6) and the corresponding eight previous models from CMIP5. The CMIP6 MME is more skillful than the CMIP5 MME in both the spatial correlation and SD of the climatological precipitation over Eastern China, related to the less SST biases in the CMIP6 models. The models with a reasonable simulation of the anticyclonic anomalies over the Western Pacific also have a higher ability in the...

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Presentation: Homogeneous and Non-Homogeneous Markov Model (Santiago) Tuesday, February 16, 2021:
2021-02-16.pdf
Abstract: Hidden Markov Model is a stochastic model that is characterized by first order Markovian transition between unobserved (hidden) states. If transitions between states are allowed to depend on an external variables, then the homogeneity of the model is relaxed and becomes a non-homogeneous hidden marking model. This model is used ti answer questions such as what is the likelihood of sequence of observations to happen given  known model, what the optimal hidden states sequence is, and what is the optimal model that maximized the probability of the observations. Brief examples of... Read more about Presentation: Homogeneous and Non-Homogeneous Markov Model (Santiago)
Group Meeting: Dynamics Associated with Atlantic Niños (Siyu) Tuesday, February 9, 2021:
group_meeting_1.pdf
Abstract: This review shows dynamics associated with Atlantic Ninos. Three mechanisms are discussed in this review. These include Bjerknes feedback (SST & westerly wind interactions), tropospheric temperature mechanism (Atmospheric thermodynamics), and ocean dynamics (upwelling Kelvin wave -> downwelling Rossby wave -> downwelling Kelvin wave). The relationship between 1997/98 El Nino and the following summer Atlantic Nino has been particularly discussed.
Group Meeting: Regional Responses of Climate to Amazon Basin Deforestation (Sarah) Tuesday, February 2, 2021
Abstract: The Amazon Basin tropical forests play important roles for climate in the area, such as storing carbon, albedo decreases, and strong evaporative cooling. However, anthropogenic deforestation from agro-industrial crops, plantations, pastures, logging, fires, etc has removed large areas of tropical forest.  Moraes et al., 2013 uses a coupled biosphere-atmosphere climate model to project changes to climate under 3 different deforestation experiments. Each deforestation experiment shows changes to the radiative balance, water cycle, and other climatic conditions. 
Group Meeting: Is the increasing fire weather risk over Western US caused by changing circulation patterns or anthropogenic warming? (Yizhou) Friday, November 13, 2020

Recent increasing wildfire activities in Western US (WUS) have raised widespread public concerns. Whether this increase is related to natural variability or anthropogenic warming is of particular interest in the research community. We observed that vapor pressure deficit (VPD), an important fire weather risk index, in the warm season (May to September) of WUS, has increased significantly since...

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Group Meeting: Climate Refugia and Conservation Implications (Mingxin) Friday, November 6, 2020:
climate_refugia_and_conservation.pptx
Refugia areas are increasingly important for conservation planning. There are two major approaches to identifying and describing refugia, patterns and processes. The responses of species to climate change are often identified using coarse-scale species distribution models (SDMs), through parameters like hydrological niche and temperature. It is crucial to develop accurate fine-scale climate grids, and identifying in situ refugia might be more appropriate for species with poor dispersal ability.
Group Meeting: ENSO Dynamics, Trends, and Prediction Using Machine Learning (Santiago) Friday, October 30, 2020:
2020-10-30.pdf
The authors of this paper used a non-homogenous Hidden Markov model (NHMM) to study ENSO dynamics and its trends within the last century as well as the capacity of the model to make predictions for the 2015-2016 El Nino. The NHMM produced 6 different hidden states that represent different well-known spatial patterns within the tropical Pacific basin from central Pacific El Nino and La Nina patterns to events confined at the eastern portion of the basin. Temporal trend for the mode that corresponded to a well defined central Pacific El Nino (often referred to as El Nino Modoki), an event that... Read more about Group Meeting: ENSO Dynamics, Trends, and Prediction Using Machine Learning (Santiago)

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