Spatial and Temporal Variability of a Latent Heat Flux in the Northwest Pacific Ocean Based on the ERA5 Reanalysis Data

Purpose. The paper is aimed at studying the spatial and temporal variability of a latent heat flux - one of the important components of heat balance in the northwestern Pacific Ocean and the Far Eastern seas based on the ERA5 5 reanalysis data.<br /> Methods and Results. The ERA5 5 reanalysis data on a latent heat flux in the area limited by the coordinates 42-60 degrees N and 135 -180 degrees E and including the Far Eastern seas and the northwestern part of the Pacific Ocean constituted the material for the study. The array of monthly averages at a quarter-degree spatial resolution was analyzed using the standard statistical methods. The average long-term distributions of latent heat flux values for each month were constructed; the amplitudes and phases of annual and semi-annual harmonics, and the linear trend coefficients were calculated in each spatial cell, and the decomposition was performed using the empirical orthogonal functions. The range of seasonal variations is significant in the zone of warm currents, and it sharply decreases in the northern part of the area under study in the Pacific Ocean as well as in the Okhotsk and Bering seas. The interannual variations are manifested in the quasi-cyclic changes of the envelope based on the maximum values with a period of about 6 years. The unidirectional trends in the interannual latent heat flux variations are weakly shown.<br /> Conclusions. . Among the seasonal variations of a latent heat flux, the annual cyclicity is predominant and the most pronounced in the southern part of the northwestern Pacific Ocean (the area influenced by the warm Kuroshio Current) off the Japan Sea coast of the Honshu Island in the Tsushima Current zone. This is conditioned by a significant evaporation increase in these areas during a cold season that, in its turn, is related to a sharper temperature contrast as well as to the impact of a winter monsoon characterized by the strong and stable northwesterly winds bringing dry, cold air from the continent. In a warm period, in some areas of the studied water area, the latent heat flux values are positive that indicates the important role of water vapor condensation in the areas with high cloudiness and in the zones of quasi- stationary upwellings.