4/1/1999 Documentation for IFA average fields: The data files in this directory have been compressed and should be transferred as binary files. The data are contained in the following five files: fields.ifa - contains basic fields as a function of pressure advect.ifa - contains advection fields as a function of pressure q1q2.ifa - contains heat and moisture fields as a function of pressure eopo.ifa - contains surface evaporation and precipitation rates misc.ifa - contains brightness temperature, SST, and surface fluxes All data in these files represent an average over the COARE Intensive Flux Array (IFA). At the perimeters of the IFA polygon were four Integrated Sounding Sites (ISS): Kapingamarangi, Manus, R/V Shiyan 3 and R/V Kexue 1. The dates when the R/V ships were present are: cruise 1: 11/10 to 12/01 cruise 2: 12/18 to 01/23 cruise 3: 01/31 to 02/18 One must realize that the representativeness of IFA averaged data is best during these three cruises and must be used with caution at other times. Fields of geopotential height (z), zonal wind (u), meridional wind (v), temperature (T) and specific humidity (q) were objectively analyzed using multiquadric interpolation (Nuss and Titley 1994) over the Large Scale Array (LSA) of TOGA/COARE at 25 mb resolution from 1000 to 25 mb and at 1 degree resolution in both the latitude and longitude directions. Surface pressure (see note below) was also analyzed over the LSA. This analyses was done for 480 six hour intervals (00, 06, 12, and 18UTC) during the COARE Intensive Observing Period (IOP - 1 November, 1992 through 28 February, 1993). Notes: - For the surface analyses: data were assumed to be surface data only if the height of the observations were within 10 m of the station height. To remove bad surface humidities (e.q., at Kapinga from 11/17/92 to 01/04/93), surface specific humidities less than 10 g/kg were removed from the analyses. Surface pressure represents pressure reduced to sea level. - The quality of the surface thermodynamic variables is suspect at some of the ISS sites (Miller and Riddle 1994) and must be used with caution. For this reason the values of Q1 and Q2 at the surface, which involves these variables, are not provided. - Negative precipitation rates, found occasionally in the file "eopo.data" result from a combination of factors: sampling errors (i.e., the inadequacy of a sounding at a given time and location to represent conditions in a large area and a longer time period), data errors, errors introduced by the objective analyses, and errors in the estimation of surface evaporation. - To keep updated on any future problems, issues and changes to the data, or to report any problems with the dataset, users are encouraged to register with Paul Ciesielski at: paulc@tornado.atmos.colostate.edu. ************************** fields.ifa ************************************** File "fields.ifa" contains 480 periods of six-hourly data. For each six hour period there are 42 lines of data. Line 1 contains: [year, month, day, hour] written with format (4i3) Line 2-42 lines contains: [p(mb), z(m), u(m/s), v(m/s), omega(mb/hr), T(C), theta(K), specific humidity(gr/kg) and divegence(1/s)*10e6] written with format (9f.2) Omega is computed using O'Brien's (1970) method with an isovalue adjustment. Omega is set to zero at the surface and at 75 mb. ************************** advect.ifa ************************************** File "advect.ifa" contains 480 periods of six-hourly data. For each six hour period there are 42 lines of data. Line 1 contains: [year, month, day, hour] written with format (4i3) Line 2-42 lines contains: [p(mb), hu(m/s**2), vu(m/s**2), hv(m/s**2), vv(m/s**2), hT(C/s), vT(C/s), hq(gr/(gr*s)), vq(gr/(gr*s))] written with format (f8.2,1p,8e11.3) where hu is the horizontal advection of u where vu is the vertical advection of u where hv is the horizontal advection of v where vv is the vertical advection of v where hT is the horizontal advection of T where vT is the vertical advection of T where hq is the horizontal advection of q where vq is the vertical advection of q These horizontal and vertical advection terms were computed using centered differences as follows: horizontal advection of "f": h(f) = u*df/dx + v*df/dy where: dx = a cos(phi)*d(lambda) dy = a d(phi) phi - latitiude lambda - longitude vertical advection of "f": v(f) = omega*df/dp ************************** q1q2.ifa ************************************** File "q1q2.ifa" contains 478 periods of six hourly data. The computation of Q1 and Q2 were not done for the first and last periods of the IOP because time center differences were used in computing these fields and no grids were analyzed before and after the IOP. For each six hour period there are 41 lines of data. No surface values of Q1 and Q2 are provided because of suspect thermodynamic data at the surface. Line 1 contains: [year, month, day, hour] written with format (4i3) Line 2-41 lines contains: [p(mb), Q1(C/day), Q2(C/day)] written with format (3f.2) The apparent heat source, Q1, and moisture sink, Q2 (Yanai et al. 1973) were computed as: Q1/cp = [dT/dt + h(T) + (p/po)**kappa * omega * d(theta)/dp] Q2/cp = -Lv/cp * [dq/dt + h(q) + v(q)] where dt = 12 hours po = 1000 mb cp = 1004 Lv = 2.5e6 g = 9.8 ************************** eopo.ifa ************************************** File "eopo.ifa" contains values of surface evaporation (e_0) and precipitation rates (p_0) for 478 six-hourly periods. The surface evaporation values represent the average from several buoys in the IFA. Once surface evaporation is known, rainfall rates can be computed from the moisture budget by integrating the equation for Q2 (shown above) from 1000 mb to 100 mb as follows: p_0 = e_0 + 1./(g*Lv) * [integral(Q2*dp) from 1000mb to 100mb] Line 1-478 contains: [year, month, day, hour, e_0(mm/day), p_0(mm/day)] written with format (4i3,2f8.2) Line 479 contains the IOP average daily rainfall rate over the IFA ************************** misc.ifa ************************************** File "misc.ifa" contains values of hourly IFA averaged miscellaneous data (IR brightness temperature, sea surface temperature and sensible and latent heat fluxes) for 480 six-hourly periods. - The IR brightness temperature data came from the Japanese GMS (courtesy of Dr. Tetsuo Nakazawa). The data is available every hour for the OOARE IOP at a spatial resolution of 11 km. Missing value flag for this field is 999.9. - The SST data, as well as, the sensible and latent heat fluxes represent the average of several buoys in the IFA. References for using this data are Lin and Johnson (1996) and Weller and Anderson (1996). The format of this data is: [year, month, day, hour, IFA average brightness temp (C), IFA average SST(C), IFA average sensible and latent heat flux (watt/(m*m)] written with format (4i5,4f8.2) A sample line from this file is shown here: 1992 11 2 6 -11.80 29.52 4.03 91.45 **************** History of dataset changes ***************************** 06/18/96 Due to very flat surface pressure (psfc) gradients over the warm pool and preceived deficiencies in the surface pressure field, the lower boundary condition was changed from omega = u*d(psfc)/dx + v*d(psfc)/dy to omega = 0. 06/18/96 Divergence and omega were corrected due to a slight error found in implementation of the O'Brien adjustment scheme. 06/18/96 Surface winds were corrected at R/V Shiyan 3 and R/V Kexue 1. Previous winds were off by 22 degrees. The 06/18/96 changes resulted in omega changes from the previous version of the analyses that were greater than 50% from the surface to 975 mb (where omegas are quite small), decreasing to less than 10% above 800 mb and to less than 1% above 500 mb. 07/06/96 Surface fields were corrected in files fields.ifa and advect.ifa on 11/09/92 at 12UTC due to some bad data that made it into the surface analyses on this day. 09/23/96: - Date/time information was corrected in file "misc.ifa". In original version of file the date associated with data at 00 UTC was incorrect. 11/13/96: - Improved surface analyses by assuming that data were from surface only if the height of the observations were within 10 m of station height. Also, bad surface humidities were removed (i.e., specific humidities less than 10 g/kg). The impact of this latter improvement will be most noteable from 11/17/92 to 01/04/93 when surface humidities at Kapinga were often considered bad (i.e., too low). The main effect of these changes, of course, are to the surface data themselves. The overall effect was to increase the IOP IFA daily averaged rainfall (estimated from the Q2 budget) from 8.166 mm/day to 8.207 mm/day (or an increase of 0.041 mm/day). *********************** References ************************************** Lin X. and R.H. Johnson, 1996: Kinematic and thermodynamic characteristics of the flow over the westerm Pacific warm pool during TOGA COARE. Accepted for publication in J. Atmos. Sci. Miller E.R. and A.C. Riddle, 1994. TOGA COARE integrated sounding system data report - Volume IA Revised Edition. Available from the TOGA-COARE International Project Office, UCAR, P.O. Box 3000, Boulder, CO 80307. Nuss W.A. and D.W. Titley, 1994: Use of multiquadric interpolation for meteorological objective analysis. Mon. Wea. Rev., 22, 1611-1631. O'Brien J.J., 1970: Alternative solutions to the classical vertical velocity problem. J. Appl. Meteor., 9, 197-203. Weller, R.A., and S.P.,Anderson, 1996: Surface meteorology and air-sea fluxes in the western Pacific during the TOGA COARE. Accepted for publication in J. Climate. Yanai, M.S., S. Esbensen and J.H. Chu, 1973: Determination of bulk properties of tropical cloud clusters form large-scale heat and moisture budgets. J. Atmos. Sci., 30, 611-627. Please send any questions or comments to Paul Ciesielski. Email: paulc@tornado.atmos.colostate.edu