<title>NOVAM evaluation from aerosol and lidar measurements in a tropical marine environment</title>

Abstract

NOVAM, the Naval Oceanic Vertical Aerosol Model, has been developed to predict the non-unifoni and nonlogarithinic extinction profiles that are often observed in the iarine atiospheric boundary layer. The kernel of NOVAN is the Navy Aerosol Model (NAN) that calculates the aerosol size distribution at 10 ii ASL froi meteorological paralueters. The aerosol profile is calculated from the surface layer size distribution with a physical model. Extinction profiles are calculated froi the aerosol profiles using a Mie code. NOVAM requires validation in different iaeteorological scenarios During the KEY9O experiient, July 1990 near Marathon (Fl), NOVAM was validated in a tropical marine environment. We ieasured the surface layer particle size distribution profile at levels froia 0.5 to 4 m ASL to evaluate the large particle end of NAN. The 110VA14 prediction of the aerosol profile in the fflixed layer was evaluated by lidar ieasurements of the 1.06 j backscatter profile. The timeserial lidar measurements show the convective pluiaes and the variability in both the aerosol content at higher levels in the boundary layer and in the boundary layer height itself. Consequences for application of NOVA?.! for slant path transmission are discussed. . INTRODUCTIONFor the assessiiient of electro-optical (EO) instruiaentation for vertical and slant path observations, knowledge on the vertical variation of electrouagnetic scattering and absorption at wavelengths froi the visible to the far infrared is important. Existing empirically derived expressions for the contribution of the aerosol to the EO propagation characteristics in the iaarine atmosphere were formulated for single levels. An exaiaple is the Navy Aerosol Model (NAN)1'2 as found in LOWTRAN VI.3 To extend the extinction prediction to higher levels, a physical model is required to calculate the vertical distribution of the aerosol. Eipirical iodels fail to predict the correct behavior see e.g., ref . 4 for a brief review) . Therefore the Naval Oceanic Vertical Aerosol Model (NOVAI4) has been developed. '' 'b, 7,t NOVAN uses neteorological profile information to account for the physical processes that influence the vertical aerosol structure and are thought to be responsible for the observed variety of profiles. NOVA!'! has been designed to describe the nonunifor but also non-logarithmic aerosol distributions that are often observed throughout the marine atiaospheric boundary layer (MABL).NOVAM is a mixture of empirical and dynamical models. The kernel for NOVAM is NAN which has been extensively updated from the original.1 NAM produces an aerosol size distribution at 10 m above the sea surface, from input data of wind speed (both current wind speed and the 24-hour average), visibility and relative hulaidity. The NANgenerated surfacelayer particle size distribution is mixed throughout the MABL by turbulent-controlled processes, further modified by humidity effects. The physics describing these processes are determined by the MABL vertical structure. Various models desc...

Modeling aerosol particle size distributions over the North Sea

“…The same applies to the water temperature. A recent analysis of aerosol measurements at locations with different water temperatures (10-30øC) has indicated that this effect may indeed be important [de Leeuw and Kunz, 1992]. The role of relative humidity must also be considered because particles grow and shrink in response to variations in this parameter.…”

The Navy Oceanic Vertical Aerosol Model

“…[7,8,9,10]. In this experiment, the surface observations were made with an instrumented fishing boat.…”