The anomaly magnitude decreases with increasing λ (Figure 13a). When τ = 12, the anomalies of the highest magnitude are found for λ = 469 nm, Δpps = − 0.04 for Stem Cell Compound Library the wide domain and − 0.025 for the domain. They become zero or positive for λ > 1240 nm. The anomaly magnitudes drop in value with solar angle (Figure 14a) from Δpps = − 0.025 for the working domain (for the broad domain Δpps = − 0.041) for ϑ = 53° to Δpps = − 0.015 (− 0.025) for ϑ = 79°. The relative anomalies (with respect to the mean surface irradiance), however, are almost constant. For the summer albedo pattern ( Figure 14b), τ = 12, h = 1 km, ϑ = 53° α = 180°, the anomaly becomes 0 (broad domain)

or positive (0.15; domain). Changing g to the ice cloud value (g = 0.75) does not influence the sign of the anomaly sign but increases its magnitude ( Figure 14b). Simulations show a large increase in the anomaly magnitude for low-base clouds, to Δpps = − 0.065 and − 0.08 for τ = 12 and h = 200 m, for the domain and the broad domain respectively. This is mainly because the cloud base and cloud top are Anti-diabetic Compound Library ic50 below some mountain peaks, which diminishes the effective cloud optical thickness in the non-uniform case. The magnitudes of the anomaly in surface irradiance due to the uniform surface

assumption are sufficiently high for it to be important for the radiative balance of the area and for estimating cloud radiative forcing. It leads to an underestimation of the surface cloud forcing in the case of plane-parallel approximation. The magnitudes of the anomaly in irradiance at the surface due to the uniform surface assumption Δpps found here are higher than the surface contribution to the plane-parallel bias (anomaly) in the atmospheric transmittance (relative downward irradiance) computed by Rozwadowska & Cahalan (2002) for variable Arctic sea ice. The anomaly magnitude for the sea-ice case was < 0.01 for τ = 15, h = 1.2 km, ϑ = 60°, λ = 605 nm and mean surface albedo 0.5. Here,

for a mean albedo of ca 0.5, τ = 12, h = 1 km, ϑ = 53° and λ = 469 nm, the anomaly magnitude is about 0.03. According to studies by Rozwadowska & Cahalan (2002), replacing a uniform cloud layer with thick non-uniform clouds further increases the magnitude of Δpps; it may double the anomaly in the case of a mean surface selleck chemical albedo of 0.5. In the case of non-uniform clouds the surface irradiance anomaly (or plane parallel bias) depends on the relative position of thicker parts of the cloud and brighter areas of the surface. When thicker clouds are more likely to occur over land (for the spring albedo pattern) or glaciers (for the summer albedo pattern), the anomaly (bias) magnitude tends to increase more than it would do so in the opposite situation or in the uncorrelated case. Channel 2 (858 nm) of the MODIS radiometer combined with channels 7 (2.13 μm) and 20 (3.75 μm) is used for cloud optical thickness and effective particle radius retrieval over the ocean ( King et al. 1997).