Mixed-layer depth is defined as SST - 1.0C.

YEAR | COUNT | |
---|---|---|

1955 | 41,958 | NODC NGOTS |

1956 | 45,978 | |

1957 | 57,427 | |

1958 | 67,380 | |

1959 | 65,886 | |

1960 | 68,758 | |

1961 | 76,295 | |

1962 | 82,125 | |

1963 | 89,042 | |

1964 | 83,430 | |

1965 | 85,909 | |

1966 | 93,860 | |

1967 | 74,938 | |

1968 | 74,305 | |

1969 | 68,484 | |

1970 | 59,781 | |

1971 | 65,320 | |

1972 | 60,205 | |

1973 | 67,360 | |

1974 | 71,294 | |

1975 | 59,659 | |

1976 | 60,606 | |

1977 | 60,171 | |

1978 | 61,217 | |

1979 | 63,189 | |

1980 | 63,715 | |

1981 | 56,893 | |

1982 | 54,920 | |

1983 | 48,150 | |

1984 | 50,863 | |

1985 | 50,294 | |

1986 | 49,072 | |

1987 | 42,969 | |

1988 | 26,260 | |

1989 | 40,092 | GTSPP |

1990 | 13,039 | |

1991 | 21,790 | |

1992 | 29,515 | |

1993 | 54,248 | |

1994 | 51,520 |

- Temperature profile databases used:
- 1955 to 1988: NODC Global Ocean Temperature/Salinity CD-ROM data set.
- 1989 to 1994: Global Temperature/Salinity Pilot Project(GTSPP) data set.

- Interpolate temperature profiles at inflection points to 15 standard levels(0, 20, 40, 60, 80, 120, 160, 200, 240, 300, 400, 500, 600, 700 and 800 meters). Simple linear interpolation is used.

- Calculate MONTHLY climatology at each standard level by BIN AVERAGING absolute temperature profiles to a 5 Deg.(X) -by- 2 Deg.(Y) grid res- olution. Only data from Jan. 1980 to Dec. 1989 was used. The MONTHLY mean was calculated for each month from 1980 to 1989. Each monthly mean is then summed over the 10 year period to form the RAW climatological mean for the month.
- A Fourier analysis is performed using the first 2 harmonics(the
ANNUAL and BI-ANNUAL cycles) for each time sequence at each grid
location for each standard depth. The Fourier series is
y'(i) = [An * COS (2*n*pi*t/12) + Bn * SIN (2*n*pi*t/12)] for n = 1 to 2 and t = 0 to 11

The Fourier coefficients A1/B1, A2/B2 and the long-term ANNUAL mean are written-out as grids at each standard level. - Areas of missing data in the Fourier coefficient and long-term ANNUAL
mean fields are filled by zonal and meridional linear interpolation.
The following procedures are followed for the area filling,
- The maximum ZONAL no-data gap is 20 degrees.
- The maximum MERIDIONAL no-data gap is 10 degrees.

- New monthly climatology fields are constructed using the filled Fourier coefficients and long-term ANNUAL mean.

- Temperature anomaly profiles are calculated using the reconstructed
monthly climatology. The climatology is BI-LINEARLY interpolated to
the location of each temperature profile and the anomalies calculated
at each standard level.
Profiles of ABSOLUTE, ANOMALOUS and CLIMATOLOGICAL temperature are saved in MONTHLY files.

- Monthly Optimum Interpolation mapping of the temperature anomalies
is performed for each standard level(0 ==> 400M) for each month from
Jan. 1955 to Dec. 1994.
Decorrelation scales used for th O.I. mapping:

ZONAL(Lx) = 10 degrees MERIDIONAL(Ly) = 5 degrees TEMPORAL(Lt) = 90 days(from the 15th of each month).

- The O.I. mapped fields are filled in space and time. The spatial
filling procedure is performed first with the following limits,
- The maximum ZONAL no-data gap is 20 degrees.
- The maximum MERIDIONAL no-data gap is 10 degrees.

- Adjust the space/time filled mapped monthly anomalies by computing the monthly MEANS of the ANOMALIES(over the period Jan. 1955 to Dec. 1994) then subtracting these means(of the anomalies) from the mapped fields.