Characteristics of the Cloud Top Heights of Marine Boundary Layer Clouds and the Frequency of Marine Fog over Mid-Latitudes

Abstract

The cloud top height of marine boundary layer clouds (MBLCs) in the mid-latitudes has received less attention than that of subtropical MBLCs and is investigated here using cloud mask data, which were based on observations from the cloud-aerosol lidar and infrared pathfinder satellite observation (CALIPSO) satellite. This study provides a comprehensive overview of the observational characteristics of variations in cloud top height of MBLCs and fog frequency over the mid-latitudes. Seasonal variations in the cloud top height of mid-latitude MBLCs as well as the differences in these seasonal variations between the Northern and Southern hemispheres were determined. For example, over the North Pacific, the cloud top height is high in winter (up to 1800 m) but low in summer (down to 800 m), whereas in the Southern Hemisphere, the seasonal variation is not well defined, with heights ranging from 1300 to 1500 m. While clear seasonal variations in the frequency of fog occurrence are found over the North Pacific and the northwest Atlantic, the fog frequency over the Southern Ocean is almost constant irrespective of the season. High correlations were found between the MBLC top height and stability indexes and between the fog frequency and some surface parameters such as temperature difference between the surface air and the sea surface. The latitudinal variations in the cloud top height of MBLCs in summer and winter over the Southern Ocean were compared with those over the North Pacific. The difference in cloud top heights between nighttime and daytime is also presented.

Data Assimilation for Climate Research: Model Parameter Estimation of Large‐Scale Condensation Scheme

“…All experiments showed general increases in estimated parameter from the default value of 0.1. Figure 8 of Kawai et al, 2015). However, some inland regions near the ocean showed shifts in values due to LETKF, which assimilates observations within the localization influence radius.…”

“…As LWP observations are available only over the ocean, parameter shifts were seen mainly over the ocean. Figure 10 of Kawai et al, 2015), and the stable atmosphere leads to slower autoconversion. Due to the smaller localization radius, LWP-L100km resulted in the finest parameter patterns.…”

“…However, the optimal parameter may be spatially different in terms of the autoconversion scheme. The cloud type and cloud thickness are different from region to region based on atmospheric stability (i.e., lower tropospheric stability [LTS]), as discussed in several previous studies (e.g., Kawai et al, 2015;Koshiro & Shiotani, 2014;Matsui, 2004;Matsui et al, 2006). The globally uniform parameter cannot reflect the dependence of the conversion speed on the cloud type and cloud geometrical thickness.…”

Radiosonde‐Derived Temperature Inversions and Their Association With Fog Over 37 Melt Seasons in East Greenland

“…IGRA‐derived FTH were compared to an independent cloud altitude data set from the CALIPSO Level 2 cloud layer product at 1 km along‐track resolution (CAL_LID_L2_01kmCLay‐Standard_V4–10 from https://www-calipso.larc.nasa.gov/). CALIPSO provides vertical profiles of aerosols and clouds with a vertical resolution of 30 m (Winker et al, ) and has been found to accurately capture fog frequency and spatial distribution when no upper clouds are present (Cermak, ; Kawai et al, ).…”

Air‐Sea exchange of biogenic volatile organic compounds and the impact on aerosol particle size distributions

“…However, the bulk of the observations fall above the blue line suggesting (1) that contributions from nonoceanic sources may be significant, (2) a breakdown in the approximation that instantaneous concentration and flux measurements are constant for multiple monoterpene lifetimes, and/or (3) a higher contribution of lower reactivity monoterpenes (e.g., camphene compared to α-pinene) to the total monoterpene signal. For comparison, the sustained monoterpene mixing ratios of 125 and 5 ppt, as observed by Yassaa et al [2008] in the Southern Ocean during in and out of bloom conditions, would require fluxes greater than 1.0 × 10 10 molecules cm À2 s À1 and 5 × 10 8 molecules cm À2 s À1 , respectively, for [O 3 ] = 20 ppb, [OH] 24h = 2.5 × 10 5 molecules cm À3 , MBL = 600 m [Kawai et al, 2015], comparable to that required in this study.…”