197 3101 6205 1002 2003 1218 2312 800 2008 0125 0956 2800 16 9 3 0 CHARACTER PORTION OF THE HEADER RECORD FOLLOWS: COLS:1-8 9-16 17-24 25-64 65-72 73-80 CKEYWORD DRWDNO VALUE DESCRIPTION (DRWDNO=Data Record Word #) UNITS KRECH 2 3101 ASCII header record, version 1 KINST 3 6205 Arecibo PR potassium lidar KINDAT 4 1002 KINDAT for ~1 min or ~20 s 3-freq night photon counts IBYRT 5 2003 beginning year for this data set IBDTT 6 1218 beginning month and day IBHMT 7 2312 beginning UT hour and minute IBCST 8 800 beginning centisecond IEYRT 9 2008 ending year for this data set IEDTT 10 0125 ending month and day IEHMT 11 0956 ending UT hour and day IECST 12 2800 ending centisecond LPROL 13 16 data record prologue length JPAR 14 9 number of single-valued parameters MPAR 15 3 number of multiple-valued parameters NROW 16 2000 number of rows of multiple-valued parameters C NROW will vary from the above value in the data records. C KODS contains the single-valued parameter(s). KODS( 1) 17 21 Day number of year (UT) 1. day KODS( 2) 18 34 Time past 0000 UT (midpoint) 1.E-03 hour KODS( 3) 19 44 Local solar time (SLT=UT+W_glon/15) 1.E-03 hour KODS( 4) 20 153 Reference geodedic latitude 1.E-02 deg KODS( 5) 21 156 Reference geodedic longitude 1.E-02 deg KODS( 6) 22 2400 Wavelength of the centroid for [K] 1.E-01 nm KODS( 7) 23 2405 Offset from the centroid frequency 1.E+05 Hz KODS( 8) 24 130 Mean azimuth angle (0=geogN,90=east) 1.E-02 deg KODS( 9) 25 140 Mean elevation angle (0=horiz,90=vert) 1.E-02 deg C KODM contains the multiple-valued parameter(s). KODM( 1) 35 110 Altitude 1. km KODM( 2) 36 111 Additional increment to 110 1.E-01 m KODM( 3) 37 2490 Photon counts (per range,altitude bin) 1. C Missing parameters are assigned a value of -32767. C Assumed parameters have an assigned error bar value of -32766. C------------------------------------------------------------------------------ CKINDAT=1002 ~67s or ~20s (pre/post-Mar06) photon counts ~0-300 km at 3 freq CKINDAT=2002 ~1 min [K] densities ~70-130 km from center frequency of counts CKINDAT=10002 ~30 min Tn values at night from ~75-115 km C------------------------------------------------------------------------------ C ARECIBO DATA USE POLICY and ACKNOWLEDGMENTS: C To offer co-authorship (part of the CEDAR DB Rules of the Road) or C acknowledgment in your publications using results from the Arecibo K lidar, C we ask that you contact the head of the Space and Atmospheric Sciences C Department at Arecibo (Sixto Gonzalez at sixto@naic.edu) or the Arecibo C scientist responsible for the potassium lidar data (Jonathan Friedman at C jonathan@naic.edu). If you use Arecibo data in your publications and C presentations, you must include this ACKNOWLEDGMENT: The Arecibo Observatory C potassium lidar is operated by the National Astronomy and Ionosphere Center C (NAIC), which is operated by Cornell University under a cooperative C agreement with the National Science Foundation. C------------------------------------------------------------------------------ C C The Arecibo potassium [K] lidar is located at Arecibo, Puerto Rico at C (18.35N, 66.75W or 293.25E), 360 m above sea level. It was developed C with CEDAR support and has been in operation since 1999. The meteoric C metallic layers, which include potassium are located between about 70 C and 120 km, with a peak near 92 km. At the end of 2001 at 92 km, the C apex magnetic lat,lon coordinates were (28.53, 10.16), where the magnetic C inclination and declination angles were 45.41 deg and -12.26 deg. C The magnetic local time at 0 UT is 1933 MLT. The solar local time (SLT) C (code 44) is UT + -66.75/15 or UT-4.45h. The data are currently only C available at night. The instrument looks in the vertical direction C (azimuth code 130 = 0 default and elevation code 140 = 9000). C C The 3-frequency lidar system uses an acousto-optic modulator, which was C invented by the CSU lidar group, to shift the laser between 3 C frequencies on the K spectrum for temperature measurements. The center C frequency Sf0 is -180 MHz from the centroid frequency of the K spectrum, C and the off center frequencies are shifted by the acousto-optic C modulators. The centroid potassium wavelength in air is at 769.898 nm C (code 2400) and is 770.1093 nm in a vacuum. The centroid frequency C (=c/wavelength) is at 389.42e+12Hz. For data prior to February 2006, C the modulated frequencies are -657.6 MHz from the centroid frequency at C Sfl (-477.6 MHz from Sf0) and +297.6 MHz at Sfh (+477.6 MHz from Sf0). C Starting in 06092, these off center frequencies changed to -421.0 MHz C and +498.0 MHz from the centroid (or -241.0 and +678.0 MHz from Sf0). C The signal Sf0 at the central line is taken first, followed by the C frequencies lower than (Sfl) and higher than (Sfh) the central line at C Sf0 (and the centroid measured by code 2405). C C The receiver system employs a GaAs photomultiplier tube (PMT) in photon C counting mode. It is protected from strong light scattering from low C altitudes by a rotating wheel shutter, which is phase locked to the C laser firing. This shutter became a permanent part of the lidar in C March 2005. Prior to that time, electronic gating of the detector was C used, but the PMT was susceptable to saturation in hazy conditions, C which required us to restrict some data sets (these are not included in C the CDB). All light below 10 km is blocked, and the shutter is fully C open at altitudes slightly above 20 km. C C The central signal Sf0 is then coupled with the off-center frequencies, C Sfl and Sfh, in the following ratios: (Sfh + Sfl)/Sf0 and Sfh/Sfl. The C former is primarly sensitive to temperature and the latter to the offset C of the spectrum from the true K spectrum. This offset can be caused by C Doppler shift, thus allowing for wind measurements, but for the Arecibo C K lidar the offset is hugely dominated by nonlinear frequency chirp in C the laser, and this ratio is used to compensate for the chirp and correct C the resulting temperature measurement. C C Integrations modes are of two types. Prior to April 2006, we were able to C pulse-to-pulse switch between laser frequencies, and thus the profiles C for all three were obtained simultaneously. At that time, 2000 laser C shots were accumulated for a data cycle, 1000 at the center frequency and C 500 at each wing frequency. The laser typically operated at 30 Hz, which C meant that it took approximately 2000/30 = 66.7 seconds to record a C profile. After changing AOMs in March 2006, we were required to use a C different integration method. A single integration for those data C consists of three separate integrations, one at each AOM state. Each C integration typically accumulates data from 600 laser pulses sent out at C 31 Hz (or 31 pulses per second), the laser rep rate having changed around C that time as well. Thus, it takes 600/31Hz = 19.355 sec to record a C signal or profile. Before the end of 2009, it took 0.5-1.5 sec to go C from one frequency to another, so the whole sequence takes a little over C 60 sec or 1 minute. However, due to characteristics of the laser (it does C not fire if the cavity is out of resonance with its seed source), the C time to take a single profile is usually longer than the ideal time of C 66.7 sec (pre-March 2006) or 19.355 sec (post-March 2006). C C The raw photon counts are stored from the ground to 300 km with a normal C range bin of 150 m. The error bar in the counts is not given but can be C calculated, as photon counting obeys Poisson statistics, to be the square C root of the counts per range bin. The height range for the raw counts is C usually 2000 bins of width 0.15 km between 0.30 to 300.15 km, while there C are 400 bins for the [K] values from 70.05 to 129.90 km, which is a C subset from #466-865 of the 2000 raw photon count range bins. The C potassium density [K] is only sampled in the first (or central) frequency, C and so has the same time as the raw photon counts when that frequency is C sampled, approximately every minute. The beginning of each frequency C profile of the raw photon counts were saved originally in Atlantic C Standard Time (AST) which is UT-4h. The Tn values were saved in SLT, C which is UT-4.45h, at the mean of all the start times of the 3 frequencies, C averaged over approximately 30 minutes (~23 frequency sets) and usually C 450 m range resolution (~3 height bins). The UT (code 34) and SLT (code 44) C times for the raw counts (and [K]) and Tn are approximate midpoint times. C C The temperature analysis and binning can be altered by the analysis code, C which will soon be available from the CEDAR Database. Temperatures >500 K C and negative values of the temperature and density were set to missing C (-32767), but it is advisable to delete Tn where the error bar exceeds C 30 K, or when the temperature is below 140 K or above 300 K. Raw counts C were set to missing for cirrus clouds around 10 km, and for bogus periods. C C Daytime observations are in the process of being implemented, and two C data sets, from June 2009, have some daytime temperatures. This is done C by adding a Faraday Anomalous Dispersion Optical Filter (FADOF) to the C receiver chain. Daytime observations are not a standard data product. C CHIST May 2011: All data were revised from 2003-2010 using consistent methods CHIST of removing the background noise and reviewing data quality. C------------------------------------------------------------------------------ C Key references for the technology of and the science derived from the C Arecibo potassium [K] lidar are: C C Friedman, J.S., S.C. Collins, R. Delgado, and P.A. Castleberg (2002), C Mesospheric potassium layer over the Arecibo Observatory, N, W, Geophys. C Res. Lett., 29(5), 1071, 10.1029/2001GL013542. C Friedman, J.S., C.A. Tepley, S. Raizada, Q.H. Zhou, J. Hedin, and R. C Delgado (2003), Potassium Doppler-resonance lidar for the study of the C mesosphere and lower thermosphere at the Arecibo Observatory, J. Atmos. C Sol. Terr. Phys., 65(16-18), 1411-1424, 10.1016/S1364-6826(03)00205-0. C Friedman, J.S., and X. Chu (2007), Nocturnal temperature structure in C the mesopause region over the Arecibo Observatory : Seasonal variations, C J. Geophys. Res., 112, D14,107, 10.1029/2006JD008220. C Friedman, J.S., X. Zhang, X. Chu, and J.M. Forbes (2009), Longitudinal C variations of the solar semidiurnal tides in the mesosphere and lower C thermosphere at low latitudes observed from ground and space, J. Geophys. C Res., 114, D11,114, 10.1029/2009JD011763. C Friedman, J.S., X. Zhang, X. Chu, and J.M. Forbes (2010), Low-latitude C thermal semidiurnal tide: longitudinal and seasonal variations based on C ground-based measurements from Arecibo and Maui, space-based measurements C by SABER, and modeling with GSWM-02, in Remote Sensing of Clouds and the C Atmosphere XV, vol. 7827, edited by R.H. Picard, K. Schaefer, A. Comeron, C and M. van Weele, SPIE, 10.1117/12.865057. C Hoeffner, J., and J.S. Friedman (2004), The mesospheric metal layer C topside: a possible connection to meteoroids, Atmos. Chem. Phys., 4, C 801-808. C Raizada, S., C.A. Tepley, D. Janches, J.S. Friedman, Q. Zhou, and C J.D. Mathews (2004), Lidar observations of Ca and K metallic layers C from Arecibo and comparison with micrometeor sporadic activity, J. C Atmos. Sol. Terr. Phys., 66, 595-606, 10.1016/j.jastp.2004.01.030. C Zhou, Q., J. Friedman, S. Raizada, C. Tepley, and Y.T. Morton (2005), C Morphology of nighttime ion, potassium and sodium layers in the meteor C zone above Arecibo, J. Atmos. Sol. Terr. Phys., 67, 1245-1257, C 10.1016/j.jastp.2005.06.013. C------------------------------------------------------------------------------ C Further questions can be addressed to: CANALYST Jonathan Friedman C Space and Atmospheric Sciences C Arecibo Observatory C HC-03 Box 53995 C Arecibo, PR 00612 C Phone: (787)-878-2612 x256 FAX: (787)-878-1861 C e-mail: jonathan@naic.edu (best) or jsf16@cornell.edu C URL: http://www.naic.edu/~lidar CANDATE May 2011