JJR 14/10/97 INTERIM PRESSURE LEVELS AND THETA LEVELS FOR UARS REFERENCE ATMOSPHERES ----------------------------------------------------------------------- Pressure levels --------------- Pressure levels are those of the UARS surfaces which are spaced at 6 surfaces per decade change in pressure: pressure = 10^(3.0-uars_surfaces/6.0) where uars_surfaces is an integer array This corresponds to an evenly spaced co-ordinate in log space. There are several ways of specifying this but an accurate way is lnp = 6.90768 + uars_surfaces*(-0.38376) where 6.90768 corresponds to UARS surface 0 (1000.0 mb). This provides an accuracy of better than 0.01% whilst conveniently ensuring that UARS surface 18 (1.00 mb) has lnp = 0.00000. Potential temperature levels ---------------------------- It was agreed that potential temperature levels should be those defined by Gloria Manney. The original note describing the production of these levels is reproduced in the next paragraph. "For each UARS pressure level, a corresponding constant potential temperature (theta) level is defined using climatological temperatures (Fleming et al., 1988). Values obtained from temperatures on the UARS pressure levels at 50N for January, 50S for July, 50N for April, and 50S for October are averaged together. "Nice" values are obtained by rounding to three significant figures, with the last significant figure being either 0 or 5." In examining these levels more closely, I have found discontinuities. I have removed two of these by setting theta(surf. 16) = 1500K (originally 1450K) theta(surf. 26) = 3900K (originally 3950K). These should be used in preference to the original levels. The pressure, log(pressure) and theta levels for the draft format atmospheres are defined here: level # pressure (mb) lnp theta(K) ------- ------------- ------- ------- 0 1000.0 6.90768 280 1 681.29 6.52392 290 2 464.16 6.14016 300 3 316.23 5.75640 315 4 215.44 5.37264 340 5 146.78 4.98888 375 6 100.00 4.60512 420 7 68.129 4.22136 465 8 46.416 3.83760 520 9 31.623 3.45384 585 10 21.544 3.07008 655 11 14.678 2.68632 740 12 10.000 2.30256 840 13 6.8129 1.91880 960 14 4.6416 1.53504 1100 15 3.1623 1.15128 1300 16 2.1544 0.76752 1500 17 1.4678 0.38376 1700 18 1.0000 0.00000 1900 19 0.68129 -0.38376 2100 20 0.46416 -0.76752 2300 21 0.31623 -1.15128 2500 22 0.21544 -1.53504 2700 23 0.14678 -1.91880 2950 24 0.10000 -2.30256 3250 25 0.068129 -2.68632 3550 26 0.046416 -3.07008 3900 27 0.031623 -3.45384 4300 28 0.021544 -3.83760 4700 29 0.014678 -4.22136 5150 30 0.010000 -4.60512 5650