Characterization of the Present-Day Arctic Atmosphere in CCSM4 Gijs de Boer 1, Bill Chapman 2, Jennifer Kay 3, Brian Medeiros 3, Matthew Shupe 4, Steve Vavrus, and John Walsh 6 (1) (2) (3) (4) ESRL () (6) CCSM Polar Climate Working Group Meeting, Boulder, CO, February 28 - March 1, 211
Goals: - Document the ability of CCSM4 to simulate the present-day Arctic atmosphere via evaluation of several key variables - SLP - Tsfc - Cloudiness - Atmospheric Energy Budget - Precipitation/Evaporation - Boundary Layer Stability - Document the ability of CCSM4 to correctly simulate variability within the system for some variables CCSM Polar Climate Working Group Meeting, Boulder, CO, February 28 - March 1, 211
Area of Study: Map courtesy of NOAA (modified) CCSM Polar Climate Working Group Meeting, Boulder, CO, February 28 - March 1, 211
Simulations: - Seven present-day AR CCSM4 simulations (6 ensemble members + MOAR) - MOAR ( Mother Of All Runs ) has high frequency output (up to 3 hourly for some variables), allowing for evaluation extremes, and monthly distributions - All simulations run at f9_g16 (.9 x1.2 ) atmosphere and land grids, gx1v6 displaced pole ocean and sea ice grids CCSM Polar Climate Working Group Meeting, Boulder, CO, February 28 - March 1, 211
Surface Temperature: - Spatial patterns simulated very well - Small but potentially important negative bias across most of Arctic - Largest negative biases east of Greenland - Largest variability between ensemble members along Barents Sea - Largest biases and smallest standard deviation during JJA - Smallest biases during FMA - RMSE of ~2-3. K -ERA-4 courtesy of Bill Chapman CCSM Polar Climate Working Group Meeting, Boulder, CO, February 28 - March 1, 211
Surface Temperature Variability: 6-hourly Temperature (K) Relative Frequency.2.1..2.1..2.1. CCSM4 ERA-4 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 24 28 24 28 24 28 24 28 -ERA-4 courtesy of Bill Chapman Temperature (K) CCSM Polar Climate Working Group Meeting, Boulder, CO, February 28 - March 1, 211
Sea Level Pressure: - Beaufort High (-1 mb bias)!! - Generally negative biases throughout Arctic (except for June) - Largest variability between ensemble members along Barents and Kara Seas during winter and spring - Largest biases and largest standard deviation during spring - Very small biases during JJA - RMSE of ~2-13 mb -ERA-4 courtesy of Bill Chapman CCSM Polar Climate Working Group Meeting, Boulder, CO, February 28 - March 1, 211
Clouds: ** Clouds are challenging to evaluate ** - Short datasets (1-2 years at a given location) - Cloud Fraction definition is not standardized, and sampling issues exist - Different thresholds used by different sensors, so we included a wide range of estimates including human, satellite and ground-based observations - Sampling -- Quick and dirty evaluation of station sampling errors provides estimate of sampling induced error (~%), but more thorough evaluation is needed and planned 11 11 11 11 1.8 1.8 1.8 1.8 9.69.69.69.6 8 8.4 8.4 8.4.4 7 7.2 7.2 7.2.2 6 4 3 6..48 4.46 3 6..48 4.46 3 6..48 4.46 3..48.46 2.44 2.44 2.44 2.44 1.42 1.42 1.42 1.42 1 1 2 2 3 3.4 1 1 2 2 3 3.4 1 1 2 2 3 3.4 1 1 2 2 3 3.4 CCSM Polar Climate Working Group Meeting, Boulder, CO, February 28 - March 1, 211
Clouds: Cloud Fraction 9 8 7 6 4 3 2 9 8 7 6 4 - Observational datasets peak during different times. - CCSM4 tends to underestimate cloud occurrence during most of the year (except summer months) - Low clouds are particularly underestimated during all but summer months (Impact of FREEZEDRY not yet fully evaluated) 3 2 2 4 6 8 1 12 Month -CloudSAT/CALIPSO dataset courtesy of Jennifer Kay -SATEST courtesy of Steve Vavrus (includes estimates from ISCCP, TOVS Path-B, HIRS, MODIS, PATMOS, Wang and Key, and CERES) -GRDEST courtesy of Steve Vavrus (includes COADS, Huschke, Hahn et al. and Makshtas et al.) -SHEBA/Bar/Eur courtesy of Matthew Shupe CCSM Polar Climate Working Group Meeting, Boulder, CO, February 28 - March 1, 211
Clouds: Water Path (gm -2 ) 3 2 1 3 2 1 3 2 Barrow Eureka SHEBA - All-sky cloud liquid/ice water paths compared to surface observation stations - CCSM4 liquid water path is too high for all locations, though seasonal cycle is captured - CCSM4 ice water path is generally too low (except for Eureka winter) - IWP seasonal cycle does not appear to be captured in the simulations - Despite a lack of clouds (CF), liquid clouds that are present are found to be too thick, particularly during summer 1 2 4 6 8 1 12 Liquid CCSM4 Month Ice OBS -Surface observations courtesy of Matthew Shupe CCSM Polar Climate Working Group Meeting, Boulder, CO, February 28 - March 1, 211
Clouds: 1 Liquid CCSM4s1 Ice Barrow Mixed Total 8 1 Liquid CCSM4 Ice SHEBA Mixed Total 8 6 1 Observations 6 4 2 Height (km) 1 1 Observations CCSM4-Obs % 4 2 2 Height (km) 1 1 CCSM4s1-Obs Std(2yr_s1) Std(ensemble) % % 2 2 4 1 1 Height (km) Fb Ap Jn Au Oc De Fb Ap Jn Au Oc De Fb Ap Jn Au Oc De Fb Ap Jn Au Oc De 1 1 Liquid Ice CCSM4 Observations CCSM4-Obs Month Eureka Mixed Total 1 2 4 % % 2 4 8 6 4 2 2 1 Fb Ap Jn Au Oc De Fb Ap Jn Au Oc De Fb Ap Jn Au Oc De Fb Ap Jn Au Oc De Month % Fb Ap Jn Au Oc De Fb Ap Jn Au Oc De Fb Ap Jn Au Oc De Fb Ap Jn Au Oc De Month CCSM Polar Climate Working Group Meeting, Boulder, CO, February 28 - March 1, 211 % -Surface observations courtesy of Matthew Shupe
Energy Budget: Wm -2 1 1 6 2 2 6 1 12 1 8 6 2 4 6 8 1 12 Month - General temporal patterns well simulated - Small differences between year period and 2 year period. - TOA radiation is under-predicted during summer months, while SFC radiation is over predicted. Too much outgoing LW at TOA (assuming incoming SW is correct). - Atmospheric energy storage during late spring/early summer is too high due in part to under-simulated fluxes into the earth s surface. E t = F rad + F sfc + F wall -JRA/NRA 21-2 and CERES from Porter et al. (21) -NRA (1979-21) and ERA-4 (1979-2) from Serreze et al. (27) CCSM Polar Climate Working Group Meeting, Boulder, CO, February 28 - March 1, 211
Precipitation/Evaporation: $*& -!- **! 3/. ##3- %2! MM DAY ")!3 ##3-34$ MM DAY MM DAY -ERA-4 courtesy of Bill Chapman CCSM Polar Climate Working Group Meeting, Boulder, CO, February 28 - March 1, 211
Lower Tropospheric Stability: % of total cases % of total cases 2 16 12 8 4 2 16 12 8 4 2 16 12 8 4 2 16 12 8 4 DJF JJA -2 2-2 2 DJF JJA Ocean MAM SON T (K) Land MAM SON - Difference between monthly mean T8 and T2m is plotted here - The atmosphere is demonstrated to be too stable for all seasons besides fall over land and ocean and possibly winter over land surfaces. - Not limited to extremely stable air (e.g. summer) - Left edge is almost always captured (exception Spring over land), but is usually under-represented. -2 2-2 2 CCSM4 CCSM3 CMIP3 T (K) ERA-4 (shading) ERA-Int (dash) -ERA-4/ERA-interim courtesy of Brian Medeiros CCSM Polar Climate Working Group Meeting, Boulder, CO, February 28 - March 1, 211
Lower Tropospheric Stability: 6-hourly Inv. Strength (K/km) CCSM4 ERA-4 Relative Frequency.1.1..1.1..1.1. Jan Feb Mar Apr 34% 32% 34% 32% 31% 3% May Jun Jul Aug 63% 74% 73% 8% 89% 77% Sep Oct Nov Dec 66% 4% 3% 8% 69% 42% 42% 4% 7% 8% 3% 3% -ERA-4/ERA-interim courtesy of Brian Medeiros 1 3 4 1 3 4 1 3 4 1 3 4 Inversion Strength (K/km) CCSM Polar Climate Working Group Meeting, Boulder, CO, February 28 - March 1, 211
Summary: The good: - Surface temperature, both spatial distribution and variability - Seasonal representation of overall energy budget The bad: - Lower tropospheric stability. Much too stable, too often - Cloud phase based on temperature dependent partitioning (gone in CESM1/CAM) - Cloud liquid water path -- severely over-simulated during summer months - Cloud ice water path -- generally under-simulated The Ugly: - Cloud fraction -- both evaluation and simulated quantity - P-E evaluation (measurements/datasets need improvement) - SLP fields demonstrating missing Beaufort High CCSM Polar Climate Working Group Meeting, Boulder, CO, February 28 - March 1, 211
EXTRA SLIDES V CCSM Polar Climate Working Group Meeting, Boulder, CO, February 28 - March 1, 211
4 2 2 4 2 1 1 Wm -2 2 6 2 2 6 1 11 1 9 2 4 6 8 1 12 Month CCSM Polar Climate Working Group Meeting, Boulder, CO, February 28 - March 1, 211