Browsing by Author "Jauregui, Yakelyn R."
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Item Open Access Modelo físico-empírico de la precipitación sobre los océanos tropicales(Instituto Geofísico del Perú, 2016-11) Jauregui, Yakelyn R.; Takahashi, KenLa precipitación mensual (P) sobre los océanos tropicales está estrechamente relacionada con la temperatura superficial del mar (TSM). Las precipitaciones intensas generalmente coinciden con TSM mayor que 27°C (Fig. 1a; Bjerknes,1969; Manabe et al., 1974; Xie 2004). Una evaluación más detallada entre ambas variables muestra que P no es sensible a la TSM cuando esta es menor que un valor crítico de TSM (Tc) de 26°C; mientras que incrementa abruptamente cuando TSM excede Tc, para luego disminuir cuando la TSM excede 30°C (Fig. 1e). Esta relación no lineal entre TSM y P ha sido confirmada con diferentes medidas de la convección como por ejemplo, intensidad nubosa (Gadgil et al., 1984), radiación de onda larga (Graham and Barnett 1987; Zhang,1993), frecuencia de reflectividad de nubes (Waliser et al., 1993), y energía potencial convectiva disponible (Williams and Renno 1993; Fu et al., 1994; Bhat et al., 1996), ha sido usada como base para esquemas simples de parametrización para estimar P usando TSM (Kleeman, 1991; Wang and Li 1993; Xie and Philander 1994; Back and Bretherton 2009). Para que la existencia de un umbral de TSM y la convección ocurran han sido asociada con la energía de inhibición convectiva (CIN) que la atmósfera requiere para activar la convección, este proceso está muy relacionado con la estabilidad vertical (Lau and Shen 1988; Johnson and Xie 2010; Johnson and Kosaka 2016).Item Restricted Simple physical‑empirical model of the precipitation distribution based on a tropical sea surface temperature threshold and the effects of climate change(Springer, 2018-03) Jauregui, Yakelyn R.; Takahashi, KenThe observed nonlinear relationship between tropical sea surface temperature (Ts) and precipitation (P) on climate timescales, by which a threshold (Tc) must be exceeded by Ts in order for deep convection to occur, is the basis of a physical-empirical model (PEM) that we fitted to observational data and CMIP5 climate model output and used to show that, with essentially only two constant parameters ( Tc and the sensitivity a1 of P to Ts>Tc ), it provides a useful first-order description of the climatological and interannual variability of the large-scale distribution of tropical P given Ts , as well as of the biases of the Global Climate Models (GCMs). A substantial limitation is its underestimation of the peak P in the convergence zones, as the necessary processes associated with the atmospheric circulation are not considered. The pattern of the intermodel correlation between the mean Ts−Tc for each GCM and the average P distribution is in agreement with the double ITCZ bias, featuring roughly zonally-symmetric off-equatorial maxima, rather than being regionally or hemispherically restricted. The inter-comparison of GCMs indicates a relationship between Tc with the near-equatorial low-level (850 hPa) tropospheric temperature, consistent with the interpretation that it is a measure of the convective inhibition (CIN). The underestimation of Tc is linked to the cold free tropospheric bias in the GCMs. However, the discrepancy among the observational datasets is a limitation for assessing the GCM biases from the PEM framework quantitatively. Under the RCP4.5 climate change scenario, Tc increases slightly more than the mean tropical Ts , implying a stabilizing trend consistent with the amplified free tropospheric warming relative to the surface. However, since a1 increases by 10–50%/ ∘ C with the surface warming, its effect dominates and results in generally positive precipitation change ( ΔP ) in the equatorial regions. In the equatorial eastern-central Pacific cold tongue, Δ(Ts−Tc) is positive, but the absolute Ts−Tc remains small, which explains the double band pattern of ΔP along the equatorial flanks of the spuriously strong double ITCZs. When the GCM biases are corrected in the PEM, the positive ΔP in the southeast Pacific and Atlantic oceans is substantially reduced.