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Investigation:

PC-06 (Betts / Maria Silva Dias / Pedro Silva Dias)

LBA Dataset ID:

PC06_ECMWF_LBA

Originator(s):

1. BETTS, A.K.
      2. JAKOB, C.

Point(s) of Contact:

ORNL DAAC User Services Office Oak Ridge National Laboratory Oak Ridge, Tennessee 37 (ornldaac@ornl.gov)

Dataset Abstract:

The Wet Season Atmospheric Mesoscale Campaign (WETAMC) of the Large-scale Biosphere-Atmosphere Experiment in Amazonia (LBA) in January and February of 1999 afforded an excellent opportunity to study the diurnal cycle of convection over land in the deep tropics [Silva Dias et al., 2000]. Surface mesomet sites and flux towers measured the diurnal thermodynamic cycle and the surface energy balance, while tethered balloons and rawinsondes probed the atmospheric above. For ground validation of the Tropical Rainfall measuring Mission (TRMM) satellite, two Doppler radars mapped the structure of evolving convective systems, and four raingage networks were installed within the scan of the ground radars [Rutledge et al., 2000]. Since the European Centre for Medium-Range Weather Forecasts (ECMWF) was closely monitoring the experiment, we took the opportunity to evaluate the surface thermodynamic cycle and diurnal cycle of precipitation in the ECMWF forecast system, using both the model operational at that time and the current operational model, which has a new land-surface scheme [Van den Hurk et al., 2000]. Earlier studies over the Mississippi basin had shown that the ECMWF model, used in the Centre's first reanalysis [Gibson et al.,1997], had deficiencies in the diurnal cycle of precipitation (it rained too early in the day), although the daily precipitation totals had only a slight high bias [Betts et al., 1998,1999]. In this paper we shall show a similar diurnal error over land in the tropics. Precipitation starts in the model only about two hours after sunrise, and it is clear from the LBA observations that this is because the morning growth of the convective boundary layer (CBL), which delays the onset of convective precipitation over the Amazon till near local noon, is not modeled correctly.

Beginning Date:

1999-01-01

Ending Date:

1999-03-31

Metadata Last Updated on:

2013-01-11

Data Status:

Archived

Access Constraints:

PUBLIC

Data Center URL:

http://daac.ornl.gov/

Distribution Contact(s):

ORNL DAAC User Services Office Oak Ridge National Laboratory Oak Ridge, Tennessee 37 (ornldaac@ornl.gov)

Access Instructions:

PUBLIC

Data Access:

IMPORTANT: The LBA-ECO Project website is no longer being supported. Links to external websites may be inactive. Final data products from the LBA project can be found at the ORNL DAAC. Please follow the fair use guidelines found in the dataset documentation when using or citing LBA data.
Datafile(s):

LBA-HMET PC-06 ECMWF Modeled Precipitation and Surface Flux, Rondonia, Brazil: 1999:  http://daac.ornl.gov/cgi-bin/dsviewer.pl?ds_id=1141

Documentation/Other Supporting Documents:

LBA-HMET PC-06 ECMWF Modeled Precipitation and Surface Flux, Rondonia, Brazil: 1999:  http://daac.ornl.gov/LBA/guides/PC06_ECMWF_LBA.html

Citation Information - Other Details:

Betts, A.K. and C. Jakob. 2013. LBA-HMET PC-06 ECMWF Modeled Precipitation and Surface Flux, Rondonia, Brazil: 1999. Data set. Available on-line [http://daac.ornl.gov] from Oak Ridge National Laboratory Distributed Active Archive Center, Oak Ridge, Tennessee, USA. http://dx.doi.org/10.3334/ORNLDAAC/1141

Keywords - Theme:

Parameter Topic Term Source Sensor
AIR TEMPERATURE ATMOSPHERE ATMOSPHERIC TEMPERATURE COMPUTER MODEL ANALYSIS
HEAT FLUX TERRESTRIAL HYDROSPHERE SOILS COMPUTER MODEL ANALYSIS
HEAT FLUX TERRESTRIAL HYDROSPHERE SURFACE WATER FIELD INVESTIGATION EDDY CORRELATION APPARATUS
HEAT FLUX TERRESTRIAL HYDROSPHERE SOILS COMPUTER MODEL ANALYSIS
HEAT FLUX TERRESTRIAL HYDROSPHERE SURFACE WATER FIELD INVESTIGATION EDDY CORRELATION APPARATUS
PRECIPITATION AMOUNT ATMOSPHERE PRECIPITATION TOWER RAIN GAUGE
PRECIPITATION AMOUNT ATMOSPHERE PRECIPITATION COMPUTER MODEL ANALYSIS

Uncontrolled Theme Keyword(s):  ATMOSPHERIC PRECIPITATIONS, COMPUTER MODELS, RONDONIA, BRAZIL, SURFACE WATERS

Keywords - Place (with associated coordinates):

Region
(click to view profile)
Site
(click to view profile)
North South East West
  BRAZILIAN AMAZON -10.75000 -10.85000 -61.87000 -62.37220

Related Publication(s):

Betts, A. K. and C. Jakob, 2002, Evaluation of the diurnal cycle of precipitation, surface thermodynamics and surface fluxes in the ECMWF model using LBA data. J. Geophys. Res., 107, 8045, doi:10.1029/2001JD000427, 2002.

Data Characteristics (Entity and Attribute Overview):

Data Characteristics:

Data for this dataset are presented in two ASCII comma separated files:

File #1: ECMWF_SCF_TESSEL.csv contains the ECMWF model output

File #2: Mean_Precip_ECMWF. csv contains the mean hourly precipitation data used to check the model output for biases.



File #1:



This is ECMWF MODEL data, run at T319 L60 with land-surface scheme TESSEL:

[ECMWF TM #295: Van den Hurk et al., 2000. This was the operational model in Fall, 2000].



Time-period of data: 1999, Day 20-60

Location: Model grid-point in Rondonia: at 10.85 deg S, 61.87 deg W

[the grid-point closest to Rondonia Abracos pasture site].

Data frequency: 20 mins

Data source: Extracted from 12-36 short term forecasts from ECMWF model



Filename: ECMWF_SCF_TESSEL.csv

File format: Comma-delimited ASCII



File contents and organization:



Column Number,Variable Name,Units/format,Variable Description,,

1,jdaydec,,Decimal time

2,idate,YYYYMMDD,Initialization date

3,itime,12,Initialization time

4,Date,YYYYMMDD,Date of forecast

5,UTC ,decimal hours,Time of forecast [end-time for fluxes]

6,UTC2,decimal hours,Relabel for 2400UTC: to identify 36h-forecast data

7,Hour,,0.5 + @INT(utc2 - 0.16666) Used for hourly means

8,DOY,,Day of Year

9,DOY2,,@IF(utc2 < 24, DOY, DOY - 1) paired with 2400 UTC time

10,Month,,Month,

11,Year,,Year,

12,k,,label for 2400UTC record in UTC2

13,T_soil_1,degrees K,Soil temperature in layer 1 (7 cm deep) reported in degrees Kelvin

14,Rad_sw_net,W/m2,Net shortwave radiation reported in Watts per meter squared(W/m2)

15,Rad_lw_net ,W/m2,Net longwave radiation reported in Watts per meter squared (W/m2)

16,LH,W/m2,Latent heat flux over water reported in Watts per meter squared (W/m2)

17,LHsnow,W/m2,Latent heat flux over ice/snow reported in Watts per meter squared (W/m2)

18,SH,W/m2,Sensible heat flux reported in Watts per meter squared (W/m2)

19,Rnet,W/m2,Net incoming radiation calculated as the sum of shortwave and longwave radiation and reported in Watts per meter squared (W/m2)

20,G,W/m2,Heat flux at the ground surface calculated as the sum of net incoming radiation, latent heat flux over water and latent heat flux over snow and reported in Watts per meter squared (W/m2)

21,G1,W/m2,Heat flux between soil layer 1 ( 7 cm deep) and soil and lower soil layers 2/3/4 reported in Watts per meter squared (W/m2)

22,SW1,m3/m3,Soil moisture in layer 1 (7 cm depth) reported in cubic meters of water per cubic meter of soil (m3/m3)

23,LSrain,mm/s,Large-scale rain reported in millimeters per second (mm/s)

24,CSrain,mm/s,Convective rain reported in millimeters per second (mm/s)

25,LSsnow,mm/s,Large-scale snow reported in millimeters per second (mm/s)

26,CSsnow,mm/s,Convective snow reported in millimeters per second (mm/s)

27,Precip_total,mm,Total precipitation calculated as 3600 * (CSrain + LSrain) and reported in millimeters (mm)

28,p0,hPa,Model surface pressure reported in hectopascals (hPa) (T-319 topography)

29,T2,degrees K,Air temperature measured at 2 meters above the soil and reported in degrees Kelvin (degrees K)

30,q2,g/kg,Specific humidity measured at 2 meters above the soil and reported in grams per kilogram (g/kg)

31,u10,m/s,Wind u-component at 10 meters above the ground reported in meters per second (m/s)

32,v10,m/s,Wind v-component at 10 meters above the ground reported in meters per second (m/s)

33,wv,m/s,Wind speed = (u10 * u10 + v10 * v10) ^ 0.5 (m/s)

34,Tskin,degrees K,Skin temperature in degrees Kelvin(K) which is equal to SST over sea

35,albedo,,Albedo reported as the proportion of visible light reflected

36,SWdown,W/m2,Downward surface solar radiation reported in Watts per meter squared (W/m2)

37,LWdown,W/m2,Downward surface longwave radiation reported in Watts per meter squared (W/m2)





[Note: Very small (.lt.1.E-10 for precipitation and .lt. 1.E-1 for radiation)

and small negative numbers in solar radiation and precipitation are

due to packing and unpacking mechanisms and do not represent model problems ]





File #2



Filename: Mean_Precip_ECMWF.csv

File format: Comma-delimited ASCII



File contents and organization:



File name:,Mean_precip_ECMWF.csv,,,,,,,,

File date:,21-Nov-12,,,,,,,,

Associated LME file:,PC06_ECMWF_LBA,,,,,,,,

,,,,,,,,,

Column,Column_heading,Units,Explanation,,,,,,

1,Year,YYYY,Sampling date: year,,,,,,

2,Month,MM,Sampling date: month,,,,,,

3,Day,DD,Sampling date: day of the month,,,,,,

4,DOY,,Sampling date reported in day of the year,,,,,,

5,UTC_hour,,Midpoint for the sampling period reported in UTC time,,,,,,

6,Decimal_day,,Sampling period reported in decimal day calculated as DOY + (UTC_hour/24),,,,,,

7,Mean_precip,mm,Mean hourly precipitation by network reported in millimeters (mm),,,,,,

,N,,Number of gauges included in the calculation of the average precipitation,,,,,,

,Network,,Network identification: networks were designated by Dr Betts,,,,,,

,,,,,,,,,

Year,Month,Day,DOY,UTC_hour,Decimal_day,Mean_precip,N,Network,

1999,1,1,1,0.5,1.02083,0,12,1,

1999,1,1,1,1.5,1.0625,0,12,1,

1999,1,1,1,2.5,1.10417,0,12,1,

1999,1,1,1,3.5,1.14583,0,12,1,

....

1999,3,31,90,20.5,90.85417,0,5,4,

1999,3,31,90,21.5,90.89583,0,5,4,

1999,3,31,90,22.5,90.9375,0,5,4,

1999,3,31,90,23.5,90.97917,0,5,4,

Data Application and Derivation:

This data set was produced to evaluate the model near-surface diurnal cycle against LBA data (Betts and Jakob, 2002a, b). The data is from a single model grid-point, centered at 10.85 deg S, 61.87 deg W. The operational model had a triangular truncation of T-319, which means it represents a grid-square of 0.5 deg on a side (see http://www.ecmwf.int/products/data/archive/data_faq.html#hres ).

The data has a time resolution of 20 mins and is continuous for days 20-60 in 1999 to coincide with the tower field measurements at the Rondonia pasture site. Note however that each day\'s data comes from a 12 to 36h short term forecast run from the 12UTC analysis from the previous day. This is considered the best model estimate of the diurnal cycle. It is close to the analysis time, so the model forecast errors are small, although as noted in the papers cited above, the model does have an error in the diurnal cycle of precipitation. Nonetheless the model fields are useful for comparison with data, for gap filling and perhaps identifying bad data records in observations, or shifts in calibration. For some fields like surface pressure, the model data is excellent.

Quality Assessment (Data Quality Attribute Accuracy Report):

Quality Assessment:

Precipitation starts about two hours after sunrise in the model, several hours earlier than observed, because the model does not simulate well the morning growth of the non-precipitating convective boundary layer. However the mean daily precipitation during the wet season compares well with observed rainfall. On most days, maximum early afternoon temperature and cloud base height are lower in the model than observed. Maximum equivalent potential temperature is close to that observed. The model surface evaporative fraction is higher than observed, and rises to near unity in the late afternoon. Work is in progress to evaluate and integrate the parameterizations for shallow and deep convection in the ECMWF model.

Process Description:

Data Acquisition Materials and Methods:

The data for this model run were collected at a pasture site located near Ouro Preto d\'Oeste, Rondonia, Brazil (about 30 km northwest of Ji-Parana) during the wet season months of January and February 1999 as part of the LBA/TRMM/WETAMC campaign. The site is part of a large deforested area (> 250 km2) dominated by a short grass (Brachiaria brizantha) with isolated palm and hardwood trees scattered throughout the landscape.



The model outputs used for comparison were 12- to 36-hour short-range forecasts, run at a triangular truncation of T319 and a vertical resolution of 60 levels, from each daily 1200 (UTC) analysis. The forecast model was the operational ECMWF model in the fall of 2000, which includes the tiled land-surface scheme (TESSEL) [Van den Hurk et al., 2000] and recent revisions to the convection, radiation, and cloud schemes described by Gregory et al., [2000]. Model data were extracted every time step at the model grid point in Rondonia closest to the field measurement site, which we shall hereinafter refer to as the Abracos pasture site (after a previous field experiment there with that name). This specific model grid point has 76 percent tall vegetation (evergreen broadleaf trees) and 24 percent low vegetation (tall grass), which is a lower percent of grass than in the region close to the pasture site. However, during the rainy season, the surface fluxes are similar over pasture and forest.

References:

Betts, A.K., P. Viterbo and E. Wood, 1998. Surface Energy and water balance for the Arkansas-Red river basin from the ECMWF reanalysis. J. Climate, 11, 2881-2897.



Betts, A.K., J.H. Ball and P. Viterbo. 1999. Basin-scale Surface Water and Energy Budgets for the Mississippi from the ECMWF Reanalysis. J. Geophys. Res., 104, 19293-19306.



Betts, A.K. and C. Jakob. 2002a. Evaluation of the diurnal cycle of precipitation, surface thermodynamics, and surface fluxes in the ECMWF model using LBA data. Journal of Geophysical Research-Atmospheres 107(D20) doi:10.1029/2001JD000427.



Betts, A.K. and C. Jakob. 2002b. Study of diurnal cycle of convective precipitation over Amazonia using a single column model. Journal of Geophysical Research-Atmospheres 107(D23) doi:10.1029/2002JD002264.



Gibson, J.K., P. Kallberg, S. Uppala, A. Hernandez, A. Nomura, E. Serrano.1997. ERA description. ECWMF Re-Analysis Project Report Series, 1, 72pp., ECMWF, Reading RG2 9AX, UK.



Rutledge, S.A., W.A. Petersen, R.C. Cifelli, L.D. Carey, 2000: Early results from TRMM-LBA: Kinematic and microphysical characteristics of convection in distinct meteorological regimes. AMS 24th 11 Conf. On Hurricanes and Tropical Meteorology. 29 May-2 June, 2000, Ft. Lauderdale, FL. 2pp.



Silva Dias, M.A., A..J. Dolman, S. Rutledge, E. Zipser, P. Silva Dias, G. Fisch, C. Nobre, P. Kabat, B. Ferrier, A. Betts, J. Halverson, M. Garstang, J. Fuentes, A. Manzi, H. Rocha, J.A. Marengo, C. Morales and N.J. Bink. 2000. Convective systems and surface processes in Amazonia during the WETAMC/LBA. BAHC News, 7, 3-7.



Van den Hurk, B.J.J.M., P. Viterbo, A.C.M. Beljaars and A. K. Betts, 2000. Offline validation of the ERA40 surface scheme. ECMWF Tech Memo, # 295. Available from ECMWF, Shinfield Park, Reading RG2 9AX, UK. 43pp.

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