import pandas as pd
import numpy as np
url='http://www.cdc.noaa.gov/Correlation/amon.us.long.data'
ts_raw = pd.read_table(url, sep=' ', skiprows=1, names=['year','jan','feb','mar','apr','may','jun','jul','aug','sep','oct','nov','dec'], skipinitialspace=True, parse_dates=True, skipfooter=4, index_col=0)                     
ts_raw.replace(-9.99900000e+01, np.NAN, inplace=True)


url='http://www.cdc.noaa.gov/Correlation/amon.us.long.data'
data = np.genfromtxt(url, skip_header=1, skip_footer=4)
nan_index = np.where(data[:]==-9.99900000e+01)
for i in range(len(nan_index[0])):
    data[nan_index[0][i], nan_index[1][i]] = np.nan
in_amo = np.mean(data[:, 1:], axis=1)

print ts_raw.values.shape
ts_raw.values

print data[:, 1:].shape
data[:, 1:]

ts_raw.values - data[:, 1:]