YANGTZE DISCHARGE MEMORY

We present a review on studies focusing on memories in hydrological time series in the Yangtze Basin basedon observational and reconstructed historical data. Memory appears as scaling of power spectra, S(f) ～f^(-β) ,with 0 <β≤ 1.The presence of scaling is noteworthy in daily river discharge time series.. 1 ) from weeks to a couple of years, power spectrafollow flicker noise, that is β≈ 1 ; 2) beyond years, spectral scaling approaches β≈ 0.3. In historical time series of floods anddroughts,power spectra also shows scaling with β≈ 0.38 ～ 0.52. Furthermore, a 70-year peak is detected in historicalmaritime events series,which also appears in other past climate indicators. Presence of memory in these hydrological timeseries implies clustering of extremes and scaling of their recurrence times, therefore, probabilistic forecast potential forextremes can be derived. On the other hand,although several physical processes, for example,soil moisture storage and highintermittency of precipitation,have been suggested to be the possible candidates contributing to the presence of long termmemory, they remain open for future research.

We present a review on studies focusing on memories in hydrological time series in the Yangtze Basin based on observational and reconstructed historical data. Memory appears as scaling of power spectra, S（f） -f^-β ,with 0 〈β≤1. The presence of scaling is noteworthy in daily river discharge time series ： 1 ） from weeks to a couple of years,power spectra follow flicker noise, that is β≈1 ; 2 ） beyond years, spectral scaling approacltesβ≈ 0. 3. In historical time series of floods and droughts,power spectra also shows scaling with β≈ 0. 38 -0.52. Furthermore, a 70-year peak is detected in historical maritime events series, which also appears in other past climate indicators. Presence of memory in these hydrological time series implies clustering of extremes and scaling of their recurrence times, therefore, probabilistic forecast potential for extremes can be derived. On the other hand, although several physical processes, for example, soil moisture storage and high intermittency of precipitation,have been suggested to be the possible candidates contributing to the presence of long term memory, they remain open for future research.