# Shading a circle along its latitude and longitude

I have a circle. I wish to shade it along its latitude and longitude as follows: Along the latitude, say starting from the point A, the color gradient should decrease until the diameter CD. Similarly from the point B(using the same color as A), the color gradient should decrease until the diameter CD. On similar lines, I need to color gradient the circle along its longitude.(Starting from C to the diameter AB and from D until the diameter AB).

\documentclass[crop,tikz,border=5mm]{standalone}
\usepackage{tikz}
\usepackage{pgfplots}
\pgfplotsset{compat=1.8}
\begin{document}
\begin{tikzpicture}
\draw (0,0) circle (2cm);
\fill[fill=black] (0,0) circle (1pt);
\node[] at (0.25,0.25) {O};
\node[] at (2.25,0.25) {C};
\node[] at (-2.25,0.25) {D};
\draw[dashed] (-2,0 ) -- (2,0);
\node[] at (0.25,2.25) {A};
\node[] at (0.25,-2.25) {B};
\draw[dashed] (0,2 ) -- (0,-2);
\end{tikzpicture}
\end{document}

• you like that shading overlaps? wit last two to cover first two? off-topic: recent version of pgfplots is 1.15 ... – Zarko Oct 15 '17 at 5:57
• overlapping is fine. – Jerry Oct 15 '17 at 6:01

you nit to clarify your demand, overlapping cause that two shadings are not visible ...

\documentclass[tikz,border=5mm]{standalone}

\begin{document}
\begin{tikzpicture}
\draw[top color=red, bottom color=white] (2,0) arc (0:180:2);
\draw[top color=white, bottom color=red] (2,0) arc (360:180:2);
\draw[left color=blue, right color=white] (0, 2) arc (90:270:2);
\draw[right color=blue, left color=white] (0,-2) arc (-90:90:2);
\fill[black] (0,0) circle (1pt) node[above right] {O};
\draw[densely dashed]
( 90:2) node[above] {A} -- (270:2) node[below] {B}
(180:2) node[left]  {D} -- (  0:2) node[right] {C};
\end{tikzpicture}

\begin{tikzpicture}
\draw[top color=red, bottom color=white, semitransparent] (2,0) arc (0:180:2);
\draw[top color=white, bottom color=red, semitransparent] (2,0) arc (360:180:2);
\draw[left color=blue, right color=white, semitransparent] (0, 2) arc (90:270:2);
\draw[right color=blue, left color=white, semitransparent] (0,-2) arc (-90:90:2);
\fill[black] (0,0) circle (1pt) node[above right] {O};
\draw[densely dashed]
( 90:2) node[above] {A} -- (270:2) node[below] {B}
(180:2) node[left]  {D} -- (  0:2) node[right] {C};
\end{tikzpicture}
\end{document}