Importance of High‐Frequency (≤30‐day) Wind Variability to the Annual Climatology of the Surface Latent Heat Flux Inferred From the Global Tropical Moored Buoy Array. Issue 3 (16th March 2022)

• Record Type: Journal Article
• Authors: Yan, Yunwei; Song, Xiangzhou; Wang, Guihua; Chen, Changlin
• Is Part Of: Journal of geophysical research. Volume 127:Issue 3(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-03-16
• Subjects: Oceanography -- Periodicals; 551.4605
• DOI: 10.1029/2021JC018094
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract: Previous studies conducted based on reanalysis data sets have suggested that high‐frequency (≤30‐day) wind variability has a significant impact on the climatology of surface latent heat flux (LHF). The present study quantifies the impact of high‐frequency winds using field measurements derived from the global tropical moored buoy array (GTMBA) and, in turn, evaluates the performance of existing reanalysis products on capturing the role of these high‐frequency winds. The buoy observations demonstrate that high‐frequency winds at the n ‐day ( n = 1, 2, …, 30) timescale make a positive contribution to the annual climatology of LHF by nonlinearly enhancing the mean surface wind speed. Furthermore, this contribution increases as the timescale decreases, with maxima occurring at the 1‐day (subdaily) timescale. The subdaily winds contribute 4.6 W m −2, on average over all GTMBA sites. The largest contribution exceeds 10.0 W m −2 over the equatorial western Pacific Ocean. Hourly reanalysis products underestimate the contribution of the high‐frequency winds at timescales shorter than about a week, especially at the subdaily timescale, which is underestimated by approximately 50–60%. This finding suggests that an improvement in the performance of subdaily wind variability is needed to improve the fidelity of next‐generation reanalysis products. Plain Language Summary: The accurate estimation of heat exchanges between the ocean and the atmosphere is critical for the proper calculation of the global ocean heat budget. To date, due to uncertainties in the estimates of surface heat fluxes, most air‐sea flux products could not close the heat budget (they typically have excessive heat fluxes into the ocean). The latent heat flux (LHF) estimates introduce the largest uncertainty in the heat budget, and this uncertainty is partly due to poor performance of the high‐frequency variability of LHF‐related variables. The present study first examines the impact that high‐frequency (≤30‐day) winds have on the LHF climatology using high temporal resolution buoy measurements collected in tropical oceans. Then it moves to evaluate the performance of existing reanalysis products. The buoy observations demonstrate that the contribution of high‐frequency winds at the n ‐day ( n = 1, 2, …, 30) timescale to the climatological annual mean LHF increases as the timescale decreases. Hourly reanalysis products were found to underestimate the contribution of high‐frequency winds at timescales shorter than about a week, especially at the 1‐day (subdaily) timescale. Improvement in the fidelity of subdaily vector winds in next‐generation reanalysis products will be helpful for reducing the excessive heat inputs into the ocean. Key Points: The contribution of n ‐day ( n = 1, 2, …, 30) timescale winds to the latent heat flux climatology increases as the timescale decreases Existing reanalysis products underestimate this contribution at timescales shorter than about 1 week, especially at subdaily timescale Improvement in the fidelity of subdaily wind variability is needed for the development of next‐generation reanalysis products