Title Meeting Name/Presenter Date OVERARCHING GOAL To develop a useful downscaled regional climate dataset to enable a variety of sectors to assess the impacts of climate variability and change. WHY DOWNSCALE? Before After CHALLENGES TO ADDRESS •Expense •Downscaling properly can be expensive. How should we perform the downscaling? •Model Uncertainty •There are many global climate models (GCMs). Which climate model should we downscale? •GCMs are imperfect. How do we address deficiencies in a given GCM? ADDRESSING THE CHALLENGE OF EXPENSE DOWNSCALING APPROCHES •Statistical (uses empirical approach: cheap but cannot resolve processes well) • Delta Method (add GCM mean change signal to present-day observations) • Bias Corrected Spatial Disaggregation (BCSD) •Dynamical (uses weather model: expensive but resolves processes well) • Classic (directly downscale uncorrected GCM) • Bias-corrected (correct the GCM with an observationally-based ‘reanalysis’ prior to dynamical downscaling) •Hybrid • Dynamically downscale lower-resolution outer domains continuously, and the higher-resolution (more expensive) domains intermittently. Then, use statistical downscaling to fill in the gaps where high resolution simulations were not dynamically downscaled. • We will employ the Hybrid approach by dynamically downscaling bias-corrected GCM output and employing BCSD to fill in the gaps. ADDRESSING THE CHALLENGE OF MODEL UNCERTAINTY There are approximately ~20 different GCM ‘families’ that support the newly released 5th Assessment Report of the Intergovernmental Panel on Climate Change (IPCC). Which one do we downscale? GCMs that best simulate presentday rainfall and temperature. Knutti et al. (2013), GRL, doi:10.1002/grl.50256 To reduce uncertainty, we will downscale the NCAR CESM/CCSM4 model because it more accurately simulates present-day climate than other global climate models. Additionally, we will bias-correct CESM/CCSM4 in order to address uncertainty due to model deficiencies. OUR MODELING APPROACH, PART 1 •Employ the Weather Research and Forecasting model (WRF) for dynamical downscaling •Nested Domains: 36-km outer domain (D1); 12-km middle domain (D2); 4-km inner domain (D3) MODEL DOMAIN OUR MODELING APPROACH, PART 2 •25-year Historical ‘Truth’ simulation from 1980-2005. WRF driven with ERA-Interim •120-year Historical+Future simulation with CCSM4 RCP8.5 simulation (‘business as usual’ emissions scenario) •50-year Future “branch” simulation with CCSM4 RCP4.5 simulation (moderate emissions scenario) MODLEING STRATEGY OUR MODELING APPROACH, PART 3 •Employ a methodology that retains the more accurate ‘mean’ state from ERA-Interim, but retains the ‘eddy’ state from CCSM4. •The ‘mean’ state is *always* a 25-year base period from 1980-2005, which ensures that the climate change signal is included in the perturbation for CCSM4. CCSM CCSM CCSM BIAS-CORRECTION METHOD ERAINT ERAINT ERAINT CCSM R ERAINT CCSM = ERA-Interim + CCSM4 EARLY RESULTS In the following slides we show results from several case studies • Tropical Cyclone Gonu, February 1-7 2007. • A wintertime “Shamal” wind event, February 2008. • A summertime month with a significant convective storm that brought rainfall, July 1995. WRF TEST SIMULATIONS: TROPICAL CYCLONE GONU, JUNE 1-7, 2007 OVERVIEW BACKGROUND •Strongest Tropical Cyclone Ever Recorded in Arabian Sea •Extensive damage to Oman, UAE, Iran and Pakistan •Imperative that we can simulate extremes such as GONU MODIS Image courtesy NASA Earth Observatory WRF TEST SIMULATIONS: TROPICAL CYCLONE GONU, JUNE 1-7, 2007 WIND TRAJECTORIES ANIMATION THIS MOVIE •Shows wind Trajectories for TC Gonu •Colors = Wind Speed (blue = slower, red = faster) WRF TEST SIMULATIONS: TROPICAL CYCLONE GONU, JUNE 1-7, 2007 RADAR REFLECTIVITY ANIMATION THIS MOVIE •Shows radar reflectivity estimate for TC Gonu •Colors = Rainfall Intensity (blues = less; reds = more) WRF TEST SIMULATIONS: TROPICAL CYCLONE GONU, JUNE 1-7, 2007 CLOUD TOP TEMPERATURE ANIMATION THIS MOVIE •Shows cloud top temperature estimate for TC Gonu •Whiter colors = higher, colder clouds •Greyer colors = lower, warmer clouds WRF TEST SIMULATIONS: TROPICAL CYCLONE GONU, JUNE 1-7, 2007 WIND SPEED ANIMATION, 1000 M ASL THIS MOVIE •Shows wind speeds for TC Gonu •Colors: blues = weaker winds; reds = stronger winds WRF TEST SIMULATIONS: TROPICAL CYCLONE GONU, JUNE 1-7, 2007 OBSERVED SATELLITE INFRARED CHANNEL VERSUS WRF ‘PSEUDO’-INFRARED CHANNEL WRF TEST SIMULATIONS: SHAMAL WIND EVENT, FEBRUARY 2008 WIND VECTORS ANIMATION, 250 M ASL THIS MOVIE •Shows vectors for Shamal wind event that occurred during the Dubai Desert Classic golf tournament •Colors: blues = weaker winds; reds = stronger winds •Note the onset of the event from the northwest MODIS Image courtesy of NASA Visible Earth WRF TEST SIMULATIONS: SUMMERTIME CONVECTION, JULY 1995 IMAGE OF WRF RAIN WATER MIXING RATIO THIS IMAGE •Shows the rainwater mixing ratio in a WRF simulation of the only convective rainfall event in July 1995. •This can be thought of as a 3-d depiction of rainfall •Demonstrates that WRF can simulate these rare but hydrologically important summer rainfall events. WRF TEST SIMULATIONS: SUMMERTIME CONVECTION, JULY 1995 IMAGE OF MONTHLY TOTAL RAINFALL: SIMULATED (COLOR FILL) VERSUS OBSERVED (DOTS) THIS IMAGE •Overall WRF can simulate the patterns of rainfall in the Oman Mountains, albeit with some biases due to displacement. CONCLUSIONS •DY ?? LNRClimateChange@ead.ae AGEDI.ae