Horizontal Wind Model 07 (HWM07) Version HWM071308E_DWM07B104i VERSION HISTORY 11 SEP 07 HWM091107E_DWM07B104i (Beta version) 13 JUL 08 HWM071308E_DWM07B104i (This version) PACKAGE CONTENTS readme.txt This file checkhwm07.f90 Test driver and test output data hwm07e.f90 Source for evaluating HWM07 dwm07b.f90 Source for evaluating disturbance wind model (DWM) apexcord.f90 Source for reading in grid and computing QD coordinates hwm071308e.dat Data file containing quiet-time HWM parameters dwm07b_104i.dat Data file containing DWM parameters apexgrid.dat Pre-computed interpolation grid for QD coordinates makefile.g95 Makefile for the g95 compiler. makefile.ifort Makefile for the Intel compiler. POINT OF CONTACT Douglas P. Drob and John Emmert Space Science Division Naval Research Laboratory 4555 Overlook Ave. Washington, DC 20375 msishwmhelp@nrl.navy.mil REFERENCES Drob, D. P., et al. (2008), An Empirical Model of the Earth's Horizontal Wind Fields: HWM07, J. Geophys Res., 113, doi:10.1029/2008JA013668. Emmert, J. T., et al. (2008), DWM07 global empirical model of upper thermospheric storm-induced disturbance winds, J. Geophys Res., 113, doi:10.1029/2008JA013541. COMPILER NOTES The model package was tested on the following FORTRAN systems: Intel (Windows, Linux), pgi (Linux), and g95 (Windows). Everything should compile cleanly using the settings given in the makefiles (e.g., make -f makefile.intel). RELEASE NOTES AND MODEL FORMULATION This is a provisional (for reasons described in the references listed above) empirical model of horizontal winds in the troposphere, stratosphere, mesosphere, and thermosphere, and is intended to succeed HWM93 [Hedin et al., J. Atmos. Terr. Phys., vol. 58, 1421-1447, 1996]. In addition to the data used in HWM93, the model is based on extensive new ground-based and space- based wind measurements, including height profiles from NASA-UARS/WINDII, NASA-UARS/HRDI, measurements from ground-based optical and radar instruments obtained from the NSF-CEDAR database, and lower atmospheric NCEP data. In the thermosphere, the model consists of two parts: a quiet-time portion, and a geomagnetically disturbed portion. The quiet-time part represents average wind conditions when ap <= 12. The disturbed part represents average perturbation winds for the specified ap input. The quiet part is represented by vector spherical harmonics in geodetic latitude, geodetic longitude, and solar local time, up to wave number 8 in latitude, 2 in longitude, and 3 in local time. The seasonal dependence is represented by harmonic terms up to semiannual. The vertical structure is represented below 250 km by cubic B-splines with node spacing of 5 km below 110 km and higher nodes at 110, 117, 125, 135, 150, 200, and 250 km. Above 250 km, an exponential decay function with a scale height of 60 km is used; continuity up to the second derivative is imposed at 250 km. The disturbance winds depend on magnetic latitude, magnetic local time, and Kp. The Quasi-Dipole magnetic coordinates described by Richmond [J Geomagn. Geoelectr., vol. 47, 191-212, 1995] are used for the magnetic coordinates; the code was obtained from the NSF-CEDAR database, and the interpolation grid was computed from IGRF at 250 km and epoch 1994.0 (a modified FORTRAN-90 version of the code, apexcord.f90, is included in this package; it contains only those subroutines needed for reading the interpolation grid and computing QD coordinates). The magnetic latitude and magnetic local time dependence of the disturbance winds is represented by vector spherical harmonics up to wave number 10 in magnetic latitude and wave number 3 in magnetic local time. At mid and low latitudes, only latitudinal terms up to wave number 4 are used; the transition from low resolution at low latitudes to high resolution at high latitudes occurs at a pre-determined latitude that depends on local time and Kp. The transition is made with an exponential function with a width of 4 degrees. The Kp dependence is represented by cubic splines with nodes at 0, 2, 5, and 8. The Kp dependence is constrained to have zero slope at Kp=0 and Kp=8, and is constant above Kp=8. The model requires three binary data files: hwm071308e.dat, dwm07b_104i.dat, and apexgrid.dat. These file should be located in the directory from which the program is run. Alternatively, the data paths can be specified explicitly via the subroutines LOADMODEL (in hwm07e.f90), LOADDWM (in dwm07b.f90), and APXRDA (in apexcord.f90), respectively. ARGUMENT CHANGES FROM HWM93 The input and output argument list remains unchanged from that of HWM93, however some of specifics of the arguments have been modified as follows: - The STL (solar local time) input argument is ignored. Local time is computed from the SEC (UT) and GLON (geographic longitude) input arguments. - Only the second element of the AP argument (the 3-hour ap) is used to compute disturbance winds. - The F107 and F107A arguments are ignored in this version. - Module component on/off switches are not yet fully implemented in this version. There is no longer a TSELEC subroutine. For now, for example if longitudinally averaged winds are desired, the model must be evaluated on a longitude grid and the output averaged by the user. MODEL LIMITATIONS AND FUTURE IMPROVEMENTS - The model currently contains no solar activity dependence, and the F107 and F107A arguments are ignored. During the day, solar activity has a relatively insignificant effect on thermospheric winds. At night, however, the effect is signficant. Solar activity dependencies will be included in a future version. - The disturbed part depends only on magnetic latitude, magnetic local time, and Kp (via the ap argument), and represents average disturbance winds in the upper thermosphere (above 225 km). The disturbance winds are assumed to be constant with height, with a smooth artificial cutoff below 125 km. Height, seasonal, and solar activity dependences will be included in a future version. TO GET TOTAL WINDS: Call HWM07 with the following input arguments: IYD - YEAR AND DAY AS YYDDD SEC - UT(SEC) ALT - ALTITUDE(KM) GLAT - GEODETIC LATITUDE(DEG) GLON - GEODETIC LONGITUDE(DEG) STL - Not used F107A - Not used F107 - Not used AP - Two element array with AP(1) = Not used AP(2) = CURRENT 3HR ap INDEX The output argument is W(1) = MERIDIONAL WIND (m/sec + Northward) W(2) = ZONAL WIND (m/sec + Eastward) TO GET QUIET TIME WINDS: Call HWM07 with a negative value for AP(2) TO GET DISTURBANCE WINDS IN GEOGRAPHIC COORDINATES: Call DWM07b_HWM_INTERFACE with the following input arguments: IYD - YEAR AND DAY AS YYDDD SEC - UT(SEC) ALT - ALTITUDE(KM) GLAT - GEODETIC LATITUDE(DEG) GLON - GEODETIC LONGITUDE(DEG) AP - Two element array with AP(1) = Not used AP(2) = CURRENT 3HR ap INDEX The output argument is DW(1) = MERIDIONAL DISTURBANCE WIND (m/sec + Geo. Northward) DW(2) = ZONAL DISTURBANCE WIND (m/sec + Geo. Eastward) TO GET DISTURBANCE WINDS IN MAGNETIC COORDINATES: Call DWM07b with the following input arguments: MLT - MAGNETIC LOCAL TIME (HRS) MLAT - MAGNETIC LATITUDE(DEG) KP - CURRENT 3HR Kp INDEX The output arguments are MMPWIND = MERIDIONAL DISTURBANCE WIND (m/sec + Magnetic Northward) MZPWIND = ZONAL DISTURBANCE WIND (m/sec + Magnetic Eastward)