Extended Data Fig. 6: Composites of daily-mean precipitation during anomalously warm and cold days at a representative location in the Gulf Stream region.
From: Signature of the western boundary currents in local climate variability
The results in Extended Data Fig. 6 explore the signature of the SST field in daily-mean precipitation as a function of precipitation amplitude, and thus indicate whether the covariability observed on month-to-month timescales arises primarily from large amplitude daily precipitation events, or from daily precipitation events across a range of amplitudes. To construct the figure, we: 1) obtained daily values of SST and precipitation (hereafter P) from the grid point identified in the inset in the figure (in the inset, the shading reproduces the vertical motion covariability from Fig. 2 panel b, and the grid point lies in a region of large SST-vertical motion covariability in the Gulf Stream region); 2) removed the seasonal-cycle and long-term trend from the SST data at the selected grid point; 3) formed composites of wintertime precipitation based on days when the SST anomaly time series at the grid point was higher than normal (SST > 1 standard deviation) and lower than normal (SST < −1 standard deviation); and 4) binned the composite precipitation values for warm and cold conditions by the amplitude of the daily-mean precipitation. The analyses are based on ~1300 days in both the SST > 1 standard deviation and SST < −1 standard deviation bins. The bars show the results as histograms, where the x-axis indicates the daily-mean precipitation amplitude and the y-axis indicates the number of days within each precipitation amplitude bin. The key result is that warm days (red bars) are marked by an increased incidence of precipitation events relative to cold days (blue bars) across a range of precipitation amplitudes. That is, they are marked by an increased incidence of not only large-amplitude precipitation events (right part of the plot) but also small amplitude events (left part of the plot). Similar conclusions emerge from analyses at other sample grid points within the different western boundary currents.
