Fig. 5: Physical mechanisms related to model uncertainties in projection.
From: Emergent constraints on future projections of the western North Pacific Subtropical High
a, c, e Intermodel spread in projected changes associated with the first principal component (PC1) and b, d, f those associated with the second principal component (PC2). a, b Sea surface temperature (SST; shadings; K) and surface temperature (Ts; shadings; K), respectively. c, d Stream function (ψ850; shadings; 106 m2 s−1) and wind (UV850; vectors drawn for larger than 0.2 m s−1) at 850 hPa, precipitation (Pr; contours in (c) drawn for ±0.2, ±0.6, and ±1.0 mm day−1), and sensible heat flux (SH; contours in (d) drawn for ±0.6, ±1.8, and ±3.0 W m−2). e, f Thickness (ΔH200–500; shadings; m) between 200 and 500 hPa and wind (UV200; vectors drawn for larger than 1 m s−1) at 200 hPa. Dotted shadings are statistically significant at the 5% level under Student t-test. Uncertainty in the equatorial western Pacific warming in (a) leads to the first uncertainty mode through the Gill-type response in (c) and (e) by triggering convective heating over the western Pacific in (c). Uncertainty related to changes in land–sea thermal contrast in (b) and associated sensible heating in (d) are responsible for the second uncertainty mode. Weakened subtropical jet stream in (f) is also manifested as a result of enhanced land–sea thermal contrast.
